Search

We present computational results on electronic, magnetic, and structural properties of CoVMnSb, a quaternary Heusler alloy. Our calculations indicate that this material may crystallize in two energetically close structural phases: inverted and regular cubic. The inverted cubic phase is the ground state, with ferrimagnetic alignment, and around 80% spin polarization. Despite having a relatively large bandgap in the minority-spin channel close to the Fermi level, this phase does not undergo a half-metallic transition under pressure. This is explained by the "pinning" of the Fermi level at the minority-spin states at the Γ point. At the same time, the regular cubic phase is half-metallic and retains its perfect spin polarization under a wide range of mechanical strain. Transition to a regular cubic phase may be attained by applying uniform pressure (but not biaxial strain). In practice, this pressure may be realized by an atomic substitution of non-magnetic atoms (Sb) with another non-magnetic atom (Si) of a smaller radius. Our calculations indicate that 25% substitution of Sb with Si results in a half-metallic regular cubic phase being the ground state. In addition, CoVMnSb0.5Si0.5 retains its half-metallic properties under a considerable range of mechanical pressure, as well as exhibits thermodynamic stability, thus making this alloy attractive for potential spintronic applications. We hope that the presented results will stimulate experimental efforts to synthesize this compound. [ABSTRACT FROM AUTHOR]

This investigation is motivated by the surge of interest in materials, combining high spontaneous magnetization and pseudocapacitance at room temperature. Ferrimagnetic MnFe 2 O 4 offers benefits of high magnetization. However, the non-pseudocapacitive behavior, low capacitance and high resistance of MnFe 2 O 4 are limiting factors for its applications in magnetic pseudocapacitive devices. This investigation demonstrates that nearly ideal pseudocapacitive behavior can be achieved for MnFe 2 O 4 electrodes in Na 2 SO 4 electrolyte. High pseudocapacitance is observed in positive and negative potential ranges and two different charging mechanisms are proposed. High capacitance is achieved at a low impedance. The ability to achieve comparable and high areal capacitances in the positive and negative potential ranges facilitates the fabrication of a symmetric pseudocapacitive device, containing ferrimagnetic MnFe 2 O 4 as cathode and anode material for operation in enlarged voltage window of 1.6 V. The symmetric device shows capacitance of 0.92 F cm−2 at a current density of 3 mA cm−2. The individual electrodes and device show good cycling stability. The approach is based on the use of murexide and gallocyanine as redox-active dispersants and charge transfer mediators. The analysis of testing results provides an insight into the influence of chemical structure, charge and redox properties of the dispersants on the capacitive behavior. The ability to fabricate a pseudocapacitive device, containing two ferrimagnetic electrodes is promising for energy storage, water purification and novel applications based on magnetocapacitive effects. [ABSTRACT FROM AUTHOR]

Cobalt doping's influence on the structural, magnetic, and electronic properties of the double spinel LiFeCr 4 O 8 was systematically investigated. Rietveld refinement revealed a consistent increase in lattice parameter a and unit cell volume with cobalt incorporation. Magnetic susceptibility measurements indicated three distinct transitions: an increase in the ferrimagnetic transition temperature (T N), a decrease in the magnetostructural transition temperature (T MS), and an increase in the spin gap transition by cobalt doping. Through diffuse reflectance spectroscopy the direct optical band gap (E og) was obtained with values of 1.169 eV, 1.303 eV, 1.396 eV, and 1.230 eV for x = 0.0, 0.1, 0.2, and 0.5, respectively. The observed increase in E og with cobalt doping suggests a widening of the band gap, which could be beneficial for optoelectronic applications. By means of X-ray photoelectron spectroscopy (XPS) the core levels of Li 1s , Co 3p , Fe 3p , Cr 3p , Fe 2p , Cr 2p , and O 1s were identified. XPS valence band (VB) analysis revealed a decreasing intensity at binding energy BE = 0 eV with respect to x = 0.0. Density functional theory calculations with Hubbard U correction (DFT + U) confirmed a ferrimagnetic semiconductor behavior with a direct electronic band gap (E eg) of 1.085 eV. [ABSTRACT FROM AUTHOR]

To realize room temperature ferromagnetic (FM) semiconductors is still a challenge in spintronics. Many antiferromagnetic (AFM) insulators and semiconductors with high Neel temperature TN are obtained in experiments, such as LaFeO3, BiFeO3, etc. High concentrations of magnetic impurities can be doped into these AFM materials, but AFM state with very tiny net magnetic moments was obtained in experiments because the magnetic impurities were equally doped into the spin up and down sublattices of the AFM materials. Here, we propose that the effective magnetic field provided by a FM substrate could guarantee the spin-dependent doping in AFM materials, where the doped magnetic impurities prefer one sublattice of spins, and the ferrimagnetic (FIM) materials are obtained. To demonstrate this proposal, we study the Mn-doped AFM insulator LaFeO3 with FM substrate of Fe metal by the density functional theory (DFT) calculations. It is shown that the doped magnetic Mn impurities prefer to occupy one sublattice of the AFM insulator and introduce large magnetic moments in La(Fe, Mn)O3. For the AFM insulator LaFeO3 with high TN = 740 K, several FIM semiconductors with high Curie temperature TC > 300 K and the band gap less than 2 eV are obtained by DFT calculations when 1/8 or 1/4 Fe atoms in LaFeO3 are replaced by the other 3d, 4d transition metal elements. The large magneto-optical Kerr effect (MOKE) is obtained in these LaFeO3-based FIM semiconductors. In addition, the FIM semiconductors with high TC are also obtained by spin-dependent doping in some other AFM materials with high TN, including BiFeO3, SrTcO3, CaTcO3, etc. Our theoretical results propose a way to obtain high TC FIM semiconductors by spin-dependent doping in high TN AFM insulators and semiconductors. [ABSTRACT FROM AUTHOR]

Spin wave propagation along a ferrimagnetic strip with out-of-plane magnetization is studied by means of micromagnetic simulations. The ferrimagnetic material is considered to be formed by two antiferromagnetically coupled sub-lattices. Two critical temperatures can be defined for such systems: that of magnetization compensation and that of angular momentum compensation, both different due to distinct Landé factors for each sub-lattice. Spin waves in the strip are excited by a spin current injected at one of its edges. The obtained dispersion diagrams show exchange-dominated forward volume spin waves. For a given excitation frequency, the Néel vector describes highly eccentric orbits, the eccentricity depending on temperature, whose semi-major axis is oriented differently at distinct locations on the FiM strip. [ABSTRACT FROM AUTHOR]

A Heat Flux Sensor (HFS) facilitates the visualization of heat flow, unlike a temperature sensor, and is anticipated to be a key technology in managing waste heat. Recently, an HFS utilizing the Anomalous Nernst Effect (ANE) has been proposed garnering significant interest in enhancing the transverse thermopower. However, ideal materials for HFS not only require a large transverse thermopower but also meet several criteria including low thermal conductivity and a bipolar nature of the transverse thermopower, especially a negative transverse thermopower. In this study, we have investigated ANE in amorphous ferrimagnetic GdCo alloys, revealing their numerous advantages as HFS materials. These include a large bipolar transverse thermopower, extremely low thermal conductivity, large negative sensitivity, versatility for deposition on various substrates, and a small longitudinal thermopower. These qualities position GdCo films as promising candidates for the advancement of HFS technology. [ABSTRACT FROM AUTHOR]

The fullerene C24 is one of the most active types of nanostructures and has been used as an active component in important applications. In this study, we investigated the magnetic characteristics of the mixed spins 5/2 and 3/2 of the Fullerene C24 system using Monte Carlo simulations. We start by offering a theoretical analysis of ground state phase diagrams. In fact, out of all potential configurations, we only present and analyze the stable configurations. Secondly, calculations are done to determine how the magnetic characteristics of this compound change as various physical parameters are changed. Additionally, we offer the examined magnetic behavior of the system with reduced temperature, reduced crystal field, reduced exchange-coupling interactions, and reduced external magnetic field. Finally, we looked into and talked about the critical reduced temperature of Fullerene C24. We showed and examined the hysteresis loops for various physical parameter values to end our work. [ABSTRACT FROM AUTHOR]

Spin pumping has significant implications for spintronics, providing a mechanism to manipulate and transport spins for information processing. Understanding and harnessing spin currents through spin pumping is critical for the development of efficient spintronic devices. The use of a magnetic insulator with low damping enhances the signal-to-noise ratio in crucial experiments such as spin-torque ferromagnetic resonance (FMR) and spin pumping. A magnetic insulator coupled with a heavy metal or quantum material offers a more straightforward model system, especially when investigating spin-charge interconversion processes to greater accuracy. This simplicity arises from the absence of unwanted effects caused by conduction electrons unlike in ferromagnetic metals. Here, we investigate the spin pumping in coupled ferrimagnetic (FiM) Y3Fe5O12 (YIG)/Tm3Fe5O12 (TmIG) bilayers combined with heavy-metal (Pt) using the inverse spin Hall effect. It is observed that magnon transmission occurs at both of the FiMs FMR positions. The enhancement of spin pumping voltage (Vsp) in the FiM garnet heterostructures is observed. The plausible reason might be the interfacial exchange coupling between FiMs. The modulation of Vsp is achieved by tuning the bilayer structure. Further, the spin mixing conductance for these coupled systems is found to be ≈ 10 18 m−2. Our findings describe a coupled FiM system for the investigation of magnon coupling providing opportunities for magnonic devices. [ABSTRACT FROM AUTHOR]

An upsurge of research activities is conducted to assess the magnetic properties of graphene nanoribbons with a keen focus on spintronic applications. The critical and compensation characteristics of mixed spin-3/2 and spin-1/2 Ising nanoribbons (Nrbs) with rectangular and hexagonal shapes under a transverse field are explored employing the finite cluster approximation. In the absence of transverse fields, only the rectangular Nrb, may exhibit one or two compensation points. This compensation persists under a transverse field Ωσ that exclusively affects the spin-1/2 of the σ-sublattice, where the order is destroyed at some Jσ-dependent critical transverse fields at T = 0. Interestingly, the insertion of a transverse field ΩS acting only on the S-sublattice, demonstrates that the order cannot be destroyed at low temperatures, with the possibility of reentrance as well as tricritical behaviors for rectangular Nrb. Finally, all these behaviors have been confirmed through an analysis of the magnetizations. [ABSTRACT FROM AUTHOR]

In this work, we shed light on the mechanism behind the complexity of the anomalous Hall effect (AHE) in the rare earth-transition metal (RE-TM) compound. To achieve a comprehensive picture, we first theoretically investigate the pure elemental metals and observe that the AHE of RE Gd is negative while that of TM Co is positive. We then investigate magnetic properties and AHE behavior for two typical cases of TM-rich and RE-rich compositions that correspond to GdCo5 and GdCo3 alloys, respectively. The observation that net magnetization is not a decisive factor in assessing the AHE value is consistent with recent claims. Besides, our investigations reveal a significant role of the Gd sublattice to the AHE. The reduction AHE signal under a high-applied field is attributed to the counteraction between the positive and negative AHC contributions when the TM and RE sub-moments are aligned parallel. On a bright note, our new findings can be successfully employed to unravel two types of aberrant humps of AHE signals near compensation temperature. [ABSTRACT FROM AUTHOR]

It is established that 2D magnetic materials are the ideal platform for building up modern-day electronic and spintronic devices. The popular ways to achieve 2D magnetic materials are mechanical exfoliation and chemical vapor deposition. However, the direct chemical synthesis route of such magnetic 2D materials on a large scale is relatively unexplored. This article reports an easy and cost-effective facile chemical synthesis with a proper capping agent and magnetic study of free-standing 2D Cr2S3 nanosheets and Cr2S3 nanoparticles within the temperature range of 2–300 K under the magnetic field of up to 5 T. Although few magnetic results on 2D Cr2S3 are available in the literature, there is enough scope to work for an in-depth understanding of the magnetic aspects of this 2D material. Here, ferrimagnetic ordering with a sufficiently high coercivity of up to 0.139 T at 2 K along with a tendency to the saturation in magnetization down to a certain temperature limit is observed. Contrary to the strong antiferromagnetic coupling with a Néel temperature, as observed by previous researchers, is also observed for this chemically synthesized 2D Cr2S3 nanosheets. A transition temperature of 117 K is observed for the Cr2S3 nanosheets, whereas for Cr2S3 nanoparticles, a transition temperature of 101.7 K is observed with negligible coercivity. This facile synthesis technique may be applied to achieve other non-van der Waals type 2D magnetic materials. These kinds of non-van der Waals type 2D magnets will be useful to modern-day spintronic devices. [ABSTRACT FROM AUTHOR]

Fully compensated ferrimagnetic half metals have attracted great attention in spintronics. Unlike many previous calculations based on hypothetical ordered alloys, here we look for existing solid solution series taking as an example Co1−xCrxS2. Calculations find that a low-spin state for Cr that matches early experiments and a fully compensated ferrimagnetic half metal with Curie temperature above room temperature is found at x ≈ 0.33. Our study demonstrates the method of combining two half metals with light and heavy 3d metals in a solid solution to achieve compensation, where atomic disorder does not destroy the desired properties. [ABSTRACT FROM AUTHOR]

In this work, we applied Monte Carlo simulations under the Metropolis algorithm to study the magnetic and magneto-caloric properties of the fullerene C 3 6 system formed with mixed spins: 2 and 5/2. We inspected the effects of not only the crystal magnetic field but also the external magnetic field and the coupling interaction between spins. In the first part, we illustrated the ground state phase diagrams in the planes of the external magnetic field, the coupling interaction between spins and the crystal magnetic field. Also, we have established these phase diagrams for null temperature. It is found that not only the total magnetizations predict the blocking temperature value t B = 5. 5 1 1 7 , but also the magnetic susceptibilities confirm this value. The effects of varying temperature values when fixing the other physical parameters have been outlined. In particular, the studied system showed a shifting between the phases the ferromagnetic phase and the paramagnetic one, at very low temperature values. [ABSTRACT FROM AUTHOR]

There is a growing interest in BiFeO3-based alloys because of the possibility it offers for developing high-temperature high-performance piezoelectric materials and for their interesting multiferroic properties. Often such ceramics are synthesized with additives either to reduce/suppress leakage current that the system inherits from the parent compound BiFeO3 or to promote sintering via formation of the liquid phase. We demonstrate here the propensity for stabilizing ferromagnetism in the ferroelectric solid solution BiFeO3–PbTiO3 (BF–PT) when synthesized with additive MnO2. Detailed investigation revealed that the ferromagnetic property of the ceramic is extrinsic and caused by the additive enabled precipitation of trace amount of the ferrimagnetic Pb-hexaferrite phase, not easily detected in conventional x-ray diffraction measurements. We also show that the ferromagnetic property is induced in Co-modified BF–PT. However, in this case, the additive stabilizes the CoFe2O4 spinel ferrite phase. While our findings offer a strategy to develop particulate magnetoelectric multiferroic composites using additive assisted precipitation of the ferrimagnetic phase(s) in BiFeO3-based ferroelectric alloys, it also helps in better understanding of the electromechanical response in BFO-based alloys. [ABSTRACT FROM AUTHOR]

Recently, we [J. Magn. Magn. Mater. 514 (2020) 167242] presented a study of the dynamic magnetic loop features of molecular-based magnetic materials and ferrimagnetism that were investigated by using a mixed spin 1/2 and spin-1 ferrimagnetic Ising system within the path probability method. We found several interesting dynamic magnetic hysteresis properties and observed that the obtained results are in qualitatively good agreement with some theoretical and experimental studies in magnetic materials. We extended our recent previous published work to study the dynamic magnetic hysteresis properties of molecular-based magnetic materials and ferrimagnetism utilizing the mixed spin (2, 5/2) ferrimagnetic Ising system on a hexagonal lattice employing the path probability method. The spin (2, 5/2) Ising system is one of the most suitable and most used prototypical systems to investigate many molecular-based magnetic materials and ferrimagnetic materials. We found more interesting dynamic magnetic hysteresis properties such as double, triple, quadruple and quintuple loop behaviors for the layer magnetization, and only double and triple loops for the total magnetization. We found that some of our obtained results are in qualitatively good agreement with some theoretical, experimental reported works, and the works on some magnetic materials as obtained by the melt-spinning technique. [ABSTRACT FROM AUTHOR]

We report the observation of unidirectional magnetoresistance (UMR) in the ferrimagnetic insulator CoFe2O4(CFO)/Pt heterostructures, which stem from the giant interfacial Rashba–Edelstein effect. Furthermore, UMR has been found to show sign reversal and amplitude enhancement characteristics with decrease in temperature. We have ascribed it to the modulated distortion of Fermi contours due to pronounced spin canting at low temperatures. The presence of spin canting induced interfacial magnetic state has also been demonstrated by spin Hall magnetoresistance in CFO/Pt/Co/Al2O3 films. Our work reveals the interfacial magnetic state modulated UMR in CFO/Pt bilayers, thereby paving the way for extending its applications in ferrimagnet-based spintronic devices. [ABSTRACT FROM AUTHOR]

Symmetry-protected band degeneracy, coupled with a magnetic order, is the key to realizing novel magnetoelectric phenomena in topological magnets. While the spin-polarized nodal states have been identified to introduce extremely-sensitive electronic responses to the magnetic states, their possible role in determining magnetic ground states has remained elusive. Here, taking external pressure as a control knob, we show that a metal-insulator transition, a spin-reorientation transition, and a structural modification occur concomitantly when the nodal-line state crosses the Fermi level in a ferrimagnetic semiconductor Mn3Si2Te6. These unique pressure-driven magnetic and electronic transitions, associated with the dome-shaped Tc variation up to nearly room temperature, originate from the interplay between the spin-orbit coupling of the nodal-line state and magnetic frustration of localized spins. Our findings highlight that the nodal-line states, isolated from other trivial states, can facilitate strongly tunable magnetic properties in topological magnets. The coupling between topological electronic properties and magnetic order offers a promising route for magnetoelectric control with great potential for both applications and fundamental physics. Here, Susilo et al demonstrate the rich tunability of magnetic properties in nodal-line magnetic semiconductor Mn3Si2Te6 using pressure as control knob. [ABSTRACT FROM AUTHOR]

Symmetry-protected band degeneracy, coupled with a magnetic order, is the key to realizing novel magnetoelectric phenomena in topological magnets. While the spin-polarized nodal states have been identified to introduce extremely-sensitive electronic responses to the magnetic states, their possible role in determining magnetic ground states has remained elusive. Here, taking external pressure as a control knob, we show that a metal-insulator transition, a spin-reorientation transition, and a structural modification occur concomitantly when the nodal-line state crosses the Fermi level in a ferrimagnetic semiconductor Mn3Si2Te6. These unique pressure-driven magnetic and electronic transitions, associated with the dome-shaped Tc variation up to nearly room temperature, originate from the interplay between the spin-orbit coupling of the nodal-line state and magnetic frustration of localized spins. Our findings highlight that the nodal-line states, isolated from other trivial states, can facilitate strongly tunable magnetic properties in topological magnets. The coupling between topological electronic properties and magnetic order offers a promising route for magnetoelectric control with great potential for both applications and fundamental physics. Here, Susilo et al demonstrate the rich tunability of magnetic properties in nodal-line magnetic semiconductor Mn3Si2Te6 using pressure as control knob. [ABSTRACT FROM AUTHOR]

Yttrium Iron Garnet (YIG) ferrites, characterized by their superior magnetic and dielectric attributes, are instrumental in advancing the development of microwave devices, particularly in enhancing high-frequency performance, integration, and miniaturization. This paper synthesizes YIG ferrite materials with the composition Bi 0.6 Y 1.4-x Ca 1+x Fe 4.5-x V 0.5 Ge x O 12 (x = 0.10 to 0.50, incrementing by 0.10) through the solid-state sintering method. It delves deeply into the mechanism by which Ca2+-Ge4+ ions substitution regulates the magnetic properties of BiV-YIG. The microstructural and magnetic properties of the samples were systematically tested and analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), vibrating sample magnetometry (VSM), and TE106 perturbation method. At a substitution content of x = 0.50, the substitution of Ge4+ ions for the Fe3+ ions at the d-site transforms the material from ferrimagnetic to paramagnetic, and the saturation magnetization of the sample drops to 132.74 G. By calculating the ferromagnetic resonance (FMR) linewidth using the law of approach to saturation, the study elucidates the negative impact of low saturation magnetization on FMR linewidth. The mechanisms proposed in this paper provide theoretical and experimental bases for reducing the FMR linewidth of high dielectric constant Bi-substituted YIG, paving the way for developing high-dielectric, low-loss YIG ferrite materials for microwave devices. [ABSTRACT FROM AUTHOR]

The dynamic magnetic and thermodynamic behaviors of the mixed-spin (1/2, 1, 3/2) Ising edge-modified graphene-like nanoparticles in a time-dependent magnetic field are studied by Monte Carlo simulation. The influence of temperature, exchange coupling, crystal field, and time-dependent magnetic field on the dynamic order parameter, magnetic susceptibility, and internal energy are investigated. The simulations reveal that the compensation behavior of the system occurs in a certain parameter range. Strong crystal field and weak exchange coupling promote the compensation behavior in the system, while increasing the amplitude of the oscillating magnetic field reduces the compensation temperature. Furthermore, the system shows the interesting multiple dynamic hysteresis behaviors under the influence of different parameters. [ABSTRACT FROM AUTHOR]

In this paper, the compensation characteristics and hysteresis loops of a ferrimagnetic mixed-spin diluted fullerene-like (XY)540 are studied based on Monte Carlo method. We show the ground-state phase diagrams in order to explore the stable configuration states. The temperature dependence of magnetization, magnetic susceptibility, internal energy, specific heat, and entropy are presented. The phase diagram including compensation temperature Tcomp and phase change temperature Tc is obtained. The multi-loop hysteresis phenomena under the influence of diverse physical parameters are observed. Finally, the critical exponents of the fullerene-like (XY)540 are obtained. [ABSTRACT FROM AUTHOR]

Perpendicularly magnetized Co-based Heusler alloys are promising candidates in high-performance spintronic devices. However, there is a contradiction between thermal stability and damping-like spin–orbit torque (SOT) efficiency in Co-based Heusler alloys with interface-induced perpendicular magnetic anisotropy (PMA). Here, we present epitaxially grown perpendicularly magnetized Mn1+xCo2−xAl (MCA) Heusler alloys through tetragonal distortion. Ferrimagnetism and distortion-induced PMA are obtained in MCA Heusler alloys. A large effective spin Hall angle (θeff) up to 0.33 is experimentally demonstrated in Pt/MCA bilayers, markedly surpassing that in conventional Pt/FM bilayers. Consequently, SOT-induced efficient magnetization switching is realized in Pt/MCA bilayers, with a critical switching current density (Jc) as low as 4 × 107 A/cm2. The large θeff and high SOT efficiency would be attributed to the staggered magnetic exchange torques in the ferrimagnetic MCA Heusler alloys. These findings demonstrate that perpendicularly magnetized ferrimagnetic MCA Heusler alloys are highly promising for high-density SOT-magnetic random-access memory with superior thermal stability and low power consumption. [ABSTRACT FROM AUTHOR]

Symmetry-protected band degeneracy, coupled with a magnetic order, is the key to realizing novel magnetoelectric phenomena in topological magnets. While the spin-polarized nodal states have been identified to introduce extremely-sensitive electronic responses to the magnetic states, their possible role in determining magnetic ground states has remained elusive. Here, taking external pressure as a control knob, we show that a metal-insulator transition, a spin-reorientation transition, and a structural modification occur concomitantly when the nodal-line state crosses the Fermi level in a ferrimagnetic semiconductor Mn3Si2Te6. These unique pressure-driven magnetic and electronic transitions, associated with the dome-shaped Tc variation up to nearly room temperature, originate from the interplay between the spin-orbit coupling of the nodal-line state and magnetic frustration of localized spins. Our findings highlight that the nodal-line states, isolated from other trivial states, can facilitate strongly tunable magnetic properties in topological magnets. The coupling between topological electronic properties and magnetic order offers a promising route for magnetoelectric control with great potential for both applications and fundamental physics. Here, Susilo et al demonstrate the rich tunability of magnetic properties in nodal-line magnetic semiconductor Mn3Si2Te6 using pressure as control knob. [ABSTRACT FROM AUTHOR]

This research focuses on the formation and assessment of sol–gel auto-combustion-produced nanocrystalline Co0.40Ni0.6AlxFe2−xO4 (x = 0.00, 0.05, 0.1, 0.2) ferrites. The investigation explores the structural, morphological, electrical, dielectric, and magnetic characteristics of the spinel ferrites sintered at different temperatures (850 °C and 950 °C), with a specific emphasis on the impact of Al3+ substitution. A cubic single-phase spinel structure exhibiting excellent crystallinity and homogeneity is found across all samples, based on XRD evaluation. The nanoparticles had typical crystallite sizes between 40 and 48 nm and average particle sizes between 122 and 186 nm. Increasing Al3+ content resulted in increased nanoparticle porosity. According to infrared spectroscopy, the adsorption band v1 rose from 538 to 554 cm−1 whereas the v2 band dropped from 374 to 366 cm−1. With an increase in Al3+ content, the experimental magnetic moment (ηexp) and saturation magnetization (Ms) of the nanoparticles showed a notable upward trend. Furthermore, the samples sintered at 950 °C displayed higher AC resistivity, attributed to a reduction of the hopping electron within the grains. All of the ferrite nanoparticles under investigation also showed high coercivity values (1028.32–1222.76 Oe), designating them as ferrimagnetic materials and emphasizing the possibility for use in spintronics, high-frequency and microwave equipment like radar, antenna, and so on. [ABSTRACT FROM AUTHOR]

NiCr2O4 nanoparticles with average particle size ∼15 nm, a single-domain size maintains the bulk canted antiferromagnetic ground state, were synthesized by a microwave combustion method. The magnetic behavior was carefully investigated by static and dynamic magnetic susceptibility measurements. In addition to a spin-glass-like behavior below paramagnetic-ferrimagnetic transition at T C, the NiCr2O4 nanoparticles demonstrate a low-temperature cluster spin glass transition below the spin canting transition T S, which manifests itself as a magnetic anomaly peak around ∼12 K (at 100 Oe) in the zero-field cooled magnetization with a relatively stronger field dependence in a 'de Almeida-Thouless' line for spin glasses. The AC susceptibility analyses in different approaches demonstrate a larger relative peak temperature variation per frequency decade and a longer characteristic relaxation time in the order of 0.04 and 10−7 s, against 0.01 and 10−9 s for the high-temperature blocking, indicating the slow spin dynamics for the low-temperature cluster glassy phase. A field-temperature magnetic phase diagram is proposed for the single-domain NiCr2O4 nanoparticles. [ABSTRACT FROM AUTHOR]

We prepared ultrafine MnCo 2 O 4 particles using a facile sol–gel autocombustion method. The structural and vibrational characterizations confirmed the formation of a pure cubic spinel phase in as-synthesized MnCo 2 O 4 particles. The surface morphology analyses revealed the porous structure with an average particle size of 5 nm and uniform distribution of manganese (Mn), cobalt (Co), and oxygen (O) in the particles. We observed the presence of multiple valence states of Mn and Co, occupying both tetrahedral and octahedral sites, enhancing our insight into the material's electronic properties and structural configuration. Our magnetization studies unveiled a Curie Temperature (T C) of 185 K with ferrimagnetic ordering below T C , resulting in substantial magnetization (9.8 emu/g) and coercivity (3.46 kOe) at 2 K and weak magnetic behavior above T C. This is attributed to the finite size and surface effects. Furthermore, the incorporation of MnCo 2 O 4 nanoparticles and graphene oxide into a polyurethane foam matrix resulted in an excellent sound absorption coefficient of 90 % at 2000 Hz. This outstanding acoustic performance underscores the versatile applications of MnCo 2 O 4 nanoparticles in diverse noise mitigation applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The atomic structures, growth patterns, new spintronic, magneto-optic, and electrical properties of 2D armchair nanoribbons of group-IV transition metal nitrides (TiN, ZrN, and HfN) have been investigated. The atomic unit cells of TiN, ZrN, HfN, TiZrN, TiHfN, and ZrHfN have been transformed into the matching armchair nanoribbons. By comparing the proposed nanoribbon to the bulk and monolayer structures of these metal nitrides, the structural stability, density, and projected density of states, band structure, magnetic behavior, and polarization were evaluated. The outcomes demonstrate that, in comparison to the crystalline structure, the suggested systems exhibit ferrimagnetic behavior and a remarkable magnetic moment. Also, a higher magnetic moment of about 24 μB in the supercells of the suggested nanoribbons was discovered due to the increased atom count. The proposed structures demonstrated indirect band gap semiconductor capabilities in the range between 1.66 eV and 2.16 eV which is again an unknown phenomenon in the bulk structure of transition metal nitrides. Owing to these characteristics, the proposed structures can be employed in many optoelectronic applications, such as solar cell devices, LEDs, laser diodes, and optical fibers where the band gap is the key requirement. Apart from this, they can also be useful in coating biomedical implanted chips, transformers, switches, and batteries. Memory storage devices will also benefit from the unique characteristics of the proposed nanoribbon structures. [ABSTRACT FROM AUTHOR]

In this work, the ion-exchange technique in molten salts was investigated to introduce copper ions in a bioactive and ferrimagnetic devitrified glass. This approach aimed to develop a magnetic and bioactive material for oncologic bone implants, able to join the ability to promote bone bonding to hyperthermic therapy while simultaneously lowering the risk of developing post-surgery infections. The ion-exchange approach was developed in order to overcome experimental critical issues related to the influence of copper introduction as a starting reagent, during the material synthesis, on magnetite nucleation. The magnetic devitrified glass was prepared by melt and quenching route, followed by ion exchange in a mixture of molten sodium and copper nitrates, in three different Na/Cu molar ratios (20, 200, 2000). The obtained samples were analysed in terms of morphology, composition, ability to release heat, bioactivity and antibacterial properties. The results revealed that copper ion-exchange involved both sodium and calcium ions and the precipitation of few amounts of copper oxide aggregates occurred. The crystalline nature of the starting material and its ability to reach the temperature needed for hyperthermia, under exposition to an alternating magnetic field, were not affected. A bacteriostatic effect was obtained by samples with the highest copper amount and the copper doping did not affect the bioactivity of the glass ceramic. [ABSTRACT FROM AUTHOR]

Ferrimagnetic Mn0.25Co0.75Fe2O4 (MCF) nanoparticles were synthesized via sol–gel autocombustion method. Polyaniline (PANI) and PANI nanocomposites with MCF as filler (PANI/MCF) were synthesized through chemical oxidative in-situ polymerization of aniline under the presence of varying weight percentage of the MCF (10%, 20% and 50%). The MCF, PANI and PANI/MCF nanocomposites were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analyzer (TGA), field emission scanning electron microscopy equipped with elemental detection (FESEM-EDAX) and vibrating sample magnetometer. The XRD and FTIR spectra confirmed the formation of pure phase with high crystallinity for all the samples. TGA study showed the increased thermal stability of PANI with addition of MCF. MCF and PANI/MCF nanocomposites showed ferrimagnetic hysteresis loop under external magnetic field at room temperature. Additionally, the ac conductivity, dielectric and electrical properties as a function of frequency ranging from 100 Hz to 120 MHz, were investigated for all the samples using impedance analyzer at room temperature. Dielectric, TGA and magnetic studies showed that PANI/MCF with 50 weight percentage of MCF has maximum ac conductivity, thermal stability and moderate magnetic properties. Hence, it could be a potential candidate to be used as dielectric material in high frequency capacitors and for electromagnetic interference shielding material at high frequency. [ABSTRACT FROM AUTHOR]

The high temperature compression experiments of 2209 duplex stainless steel were carried out by using Glee-ble3800 thermal simulator, the rate was 0,01~10 s-1, and the deformation temperature was 950~1 100°C. The strain rate and deformation temperature were analyzed and the effect of strain rate and deformation temperature were analyzed. The high-temperature rheological behavior of 2209 duplex stainless steel was investigated, and the effects of strain rate and deformation temperature on the two-phase relationship of 2209 duplex stainless steel were analyzed, the strain rate compensation factor Z was introduced, and the Arrhenius eigenmodel equation was established. The results show that the theoretical value of peak stress calculated numerically by this constitutive model fits well with the experimental results, and the correlation is 97,3 %, which verifies the feasibility of the model. [ABSTRACT FROM AUTHOR]

The anomalous Nernst effect (ANE) has garnered significant interest for practical applications, particularly in energy harvesting and heat flux sensing. For these applications, it is crucial for the module to operate without an external magnetic field, necessitating a combination of a large ANE and a substantial coercive force. However, most materials exhibiting a large ANE typically have a relatively small coercive force. In our research, we have explored the ANE in amorphous ferrimagnetic TbCo alloy films, noting that the coercive force peaks at the magnetization compensation point (MCP). We observed that transverse Seebeck coefficients are amplified with Tb doping, reaching more than 1.0 μV/K over a wide composition range near the MCP, which is three times greater than that of pure Co. Our findings indicate that this enhancement is primarily due to direct conversion, a product of the transverse thermoelectric component and electrical resistivity. TbCo films present several significant advantages for practical use: a large ANE, the capability to exhibit both positive and negative ANE, the flexibility to be deposited on any substrate due to their amorphous nature, a low thermal conductivity, and a large coercive force. These attributes make TbCo films a promising material for advancing ANE-based technologies. [ABSTRACT FROM AUTHOR]

The exchange integral in the magnetic response of a spherical metallic iron (Fe) and nickel (Ni) nanoparticle is theoretically studied by using Monte Carlo simulations. To this end, using the nanoparticles model in spherical coordinates, we compute magnetization, magnetic susceptibility, specific heat, internal energy, and hysteresis loop over a wide range of temperatures for an Fe and Ni nanoparticle with a size of about 2 nm. The phase transition temperatures are interpolated versus the exchange parameters, and it is observed that the dependence on the coupling parameter is completely linear. Moreover, from the susceptibility results of the samples, the sharpest peak with the least fluctuation gives us the most appropriate Curie temperature and exchange integral for this system. However, the peak related to the heat capacity is also in the Curie temperature range. From the internal energy results, it can be understood that with the increase in phase transition and interaction, the system reaches equilibrium. The magnetic coercive field and remanent magnetization caused by nanoparticles indicate superparamagnetic properties at room temperature. At the end, the obtained results allow us to theoretically determine the magnetic properties of spherical nanoparticles and pave the way for the development of nanoparticles for many applications. [ABSTRACT FROM AUTHOR]

Magnetic fibers were synthesized by the lumen loading method using bamboo fibers as a cellulose source and cobalt ferrite nanoparticles with polyethylenimine (PEI) as a retention aid. Bamboo fiber is a significant fibrous raw material, and cobalt ferrite particles are suitable for magnetic modification. The resulting composite retained the intrinsic features of cellulose fiber while gaining the magnetic properties of nanoparticles. Cobalt ferrite nanoparticles were synthesized using a sol–gel technique and coated with tetraethyl orthosilicate (TEOS) molecules before being functionalized with PEI. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and vibrating-sample magnetometry (VSM) were used to characterize the samples. The nanoparticles produced had an inverse cubic spinel crystalline structure and exhibited ferrimagnetic activity. The coercivity value for modified fiber produced was greater than 200 Oe, indicating that it may be utilized for magnetic recording. Lumen-Loading procedure of CoFe2O4-SiO2-PEI on the disintegrated bamboo fibers [ABSTRACT FROM AUTHOR]

In our studies, we combined two powdered materials, i.e., ferroelectric triglycine sulfate (TGS) and ferrimagnetic magnetite Fe3O4, to obtain a magnetoelectric composite. The ferroelectric (E) part, i.e., TGS, was a hybrid organic–inorganic crystal, which we obtained as a pure single crystal from an aqueous solution using a static water evaporation method. The magnetic (M) part of the composite was commercially available magnetite. The samples used for the dielectric and magnetoelectric measurements were cold-pressed and made in the form of a circular tablet. The measuring electrodes were made of silver-based conductive paste and were attached to the sample. We measured the temperature dependencies of selected electrical parameters (e.g., dielectric permittivity, electrical capacity, and loss angle tangent). We used the dynamic lock-in method to check whether magnetoelectric coupling existed between the E and M phases. In this paper, we present the dielectric properties of pure monocrystalline TGS as a reference sample and compare the results for TGS powder, TGS + carbon powder, and TGS + Fe3O4 powder. The magnetoelectric coupling presumably appeared for the composite TGS + 10 wt. % Fe3O4, as evidenced by the shift in the phase transition temperature in the TGS. Moreover, the theoretical interpretation of the effect is proposed. [ABSTRACT FROM AUTHOR]

Magnetic skyrmions with nontrivial topologies have great potential to serve as memory cells in novel spintronic devices. Small skyrmions were theoretically and experimentally confirmed to be generated under the influence of external fields in ferrimagnetic films via Dzyaloshinskii–Moriya interactions (DMIs). However, this topological state has yet to be verified in ferrimagnetic crystals, especially in the absence of external fields and DMIs. Here, spontaneous biskyrmions were directly observed in the Tb0.2Gd0.8Co2 ferrimagnetic crystal with a Kagome lattice using Lorentz transmission electron microscopy. The high-density biskyrmions exhibited a small size (approximately 50 nm) over a wide temperature range, were closely related to subtle magnetic interaction competition, and coexisted with some broken stripes that could be easily converted into zero-field biskyrmions by utilizing proper field-cooling manipulation. These results can be used to establish a platform for investigating functional sub-50-nm skyrmions in ferrimagnetic crystals and to facilitate advanced applications in magnetic devices. Revolutionising Spintronics: Zero-Field Biskyrmions in Ferrimagnetic Kagome Lattice Scientists have found a new method to control small skyrmions, which are tiny magnetic patterns, in ferrimagnetic materials (materials that have a net magnetic moment even without an external magnetic field arising from the two opposite magnetic sublattices). The research, led by S.L. Zuo and K.M. Qiao, revealed that these skyrmions can be maintained in ferrimagnetic materials without requiring an external magnetic field. The researchers used a technique called Lorentz transmission electron microscopy to observe the skyrmions in a specific ferrimagnetic crystal, Tb0.2Gd0.8Co2. They discovered that the skyrmions remained stable across a broad temperature range and could be easily controlled by altering the temperature or applying a minor magnetic field. This finding could be crucial for the creation of future spintronic devices, devices that use the rotation of electrons to store and process data. This summary was initially drafted using artificial intelligence, then revised and fact-checked by the author. [ABSTRACT FROM AUTHOR]

Orbital currents play a fundamental role in a wide range of transport phenomena. Recently, the discovery of a novel chiral orbital current state in the ferrimagnetic nodal-line semiconductor Mn3Si2Te6 has attracted significant interest, supported by anomalous I–V characteristics and time-dependent bistable switching. However, the direct experimental verifications, combining electrical transport and magnetic measurement, that detect the variation of the magnetic properties vs the current are still rare. Here, we investigate the transport properties of Mn3Si2Te6 and track the current-induced dynamics of the magnetic moment. Reflective magnetic circular dichroism reveals that significant alterations in Mn3Si2Te6 magnetoresistance in response to an electric field are necessarily coupled with a magnetic phase transition, establishing a rare correlation. Our findings indicate the predominance of magnetic chiral orbital currents in the colossal angular magnetoresistance effect, offering a unique platform for advanced studies in orbital magnetism. [ABSTRACT FROM AUTHOR]

Polycrystalline [(0.5) Bi0.5Na0.5TiO3-(0.5) LaFeO3] multiferroic composite is prepared by using the solid-state reaction method. The crystal structure of both phases is characterized by using the X-ray diffraction method (XRD) and confirms the presence of rhombohedral (i.e., bismuth sodium titanate) and orthorhombic (i.e., lanthanum ferrite) phases in the composite. The microstructure of the composite is analyzed using field emission scanning electron microscopy (FESEM). The crystal structure is further studied with Raman spectroscopy. The present composite exhibits ferroelectric and ferrimagnetic-like properties, revealing its multiferroic behavior. Furthermore, the impedance analysis of the composite shows the negative temperature coefficient of resistance behavior. The present study describes the structural and physical properties of the possible lead-free multiferroic composite. [ABSTRACT FROM AUTHOR]

Orbital currents play a fundamental role in a wide range of transport phenomena. Recently, the discovery of a novel chiral orbital current state in the ferrimagnetic nodal-line semiconductor Mn3Si2Te6 has attracted significant interest, supported by anomalous I–V characteristics and time-dependent bistable switching. However, the direct experimental verifications, combining electrical transport and magnetic measurement, that detect the variation of the magnetic properties vs the current are still rare. Here, we investigate the transport properties of Mn3Si2Te6 and track the current-induced dynamics of the magnetic moment. Reflective magnetic circular dichroism reveals that significant alterations in Mn3Si2Te6 magnetoresistance in response to an electric field are necessarily coupled with a magnetic phase transition, establishing a rare correlation. Our findings indicate the predominance of magnetic chiral orbital currents in the colossal angular magnetoresistance effect, offering a unique platform for advanced studies in orbital magnetism. [ABSTRACT FROM AUTHOR]

A high temperature MD effect has been observed in Pr3Fe5O12 (PrIG) which is a new member of rare earth iron garnets (RIG) family. Research indicates that this material has two dielectric relaxations in the temperature range from 370 K to 565 K and a dielectric anomaly around 580 K. The first dielectric relaxation is attributed to the conduction for the similar activation energy with conduction. The other dielectric relaxation in the higher temperature range originated from the inhomogeneous structure. And, the coupling between the ferrimagnetic phase transition and the dielectric response was observed at 1 kHz 0.35 T 580K. [ABSTRACT FROM AUTHOR]

Background: Adjuvant administration of hyperthermia (HT) with radiation therapy in the treatment of cancer has been extensively studied in the past five decades. Concurrent use of the two modalities leads to both complementary and synergetic enhancements in tumor management, but presents a practical challenge. Their simultaneous administration using the same implantable thermo‐brachytherapy (TB) seed source has been established theoretically through magnetically mediated heat induction with ferromagnetic materials. Careful consideration, however, showed that regular ferromagnetic alloys lack the required conductivity to generate enough power through eddy current to overcome heat dissipation due to blood perfusion at clinically measured rates. Purpose: We characterized the TB implant that combines a sealed radioactive source with a ferrimagnetic ceramic (ferrite) core, serving as a self‐regulating HT source when placed in an alternating electromagnetic field. To increase the heat production and uniformity of temperature distribution the empty spacers between radioisotope seeds were replaced by hyperthermia‐only (HT‐only) seeds. Methods: The heat generation due to eddy currents circulating in the seed's thin metal shell, surrounding the core, depends drastically on the core permeability. We identified a soft ferrite material (MnZnFe2O4$\rm MnZnFe_2O_4$) as the best candidate for the core, owing to its high permeability, the HT‐range Curie temperature, adjustable through material composition, and a sharp Curie transition, leading to heat self‐regulation, with no invasive thermometry required. The core permeability as a function of temperature was calculated based on measured resistor‐inductor (RL) circuit parameters and material B‐H curves. The thickness of the shell was optimized separately for TB and HT‐only seeds, having slightly different dimensions. Heat generation was calculated using the power versus temperature approximation. Finally, the temperature distribution for a realistic prostate LDR brachytherapy plan was modeled with COMSOL Multiphysics for a set of blood perfusion rates found in the literature. Results: The small size of the investigated ferrite core samples resulted in demagnetization significantly decreasing the relative permeability from its intrinsic value of ∼5000 to about 11 in the range of magnetic field amplitude and frequency values relevant to HT. The power generated by the seed dropped sharply as the shell thickness deviated from the optimal value. The optimized TB and HT‐only seeds generated 45 and 267 mW power, respectively, providing a HT source sufficient for >90% volume coverage even for the highest blood perfusion rates. The toxicity of the surrounding normal tissues was minimal due to the rapid temperature fall off within a few millimeters distance from a seed. Conclusions: The investigated TB and HT‐only seed prototypes were shown to provide sufficient power for the concurrent administration of radiation and HT. In addition to being used as a source for both radiation and heat at the onset of cancer therapy, these implanted seeds would be available for treatment intensification in the setting of salvage brachytherapy for locally radiorecurrent disease, possibly as a sensitizer to systemic therapies or as a modulator of the immune response, without another invasive procedure. Experimentally determined parameters of the ferrite material cores provided in this study establish a mechanistic foundation for future pre‐clinical and clinical validation studies. [ABSTRACT FROM AUTHOR]

Half‐metallic ferromagnets (HMFs) are highly desirable materials for applications in spintronics because of their semiconducting behavior for one spin projection and metallic nature for the other. To operate spintronic devices at room temperature (RT), HMFs should simultaneously have a large saturation magnetization (MS), high magnetic Curie temperature (TC), and a wide half‐metallic gap. However, HMFs that simultaneously fulfill these three criteria are rare. In this work, we report for the first time on the ferrimagnetic double perovskite oxides of Sr2CrHfO6 (SCHO) with a magnetic TC up to 545 K due to the strong Cr3+(↑)Cr4+(↓) antiferromagnetic spin interactions. The combined experimental results confirmed that the SCHO powders crystallized in an orthogonal crystal structure with Pnma symmetry. The SEM images demonstrate that the powders exhibit a spherical morphology with particle sizes between 150 and 250 nm. XPS spectra verified the presence of Sr2+, Cr 3+/Cr4+, and Hf4+/Hfx+ (x < 4) ions in the SCHO powder. Oxygen was present as lattice oxygen and adsorbed oxygen species. At 2 K, the SCHO powder exhibited ferrimagnetic behavior with MS of 0.11 μB/f. u and a magnetic coercive field of 290 Oe. The SCHO ceramics displayed a normal butterfly‐like magnetoresistance‐magnetic field (MR‐H) curve at 2 K due to the intergranular tunneling effect, and the MR (2 K, 7 T) value was −2.05%. The temperature dependence of the resistivity of the SCHO ceramics revealed their semiconducting nature, and the electrical transport data in the temperature range 2−800 K were well fitted by the Mott's variable‐range hopping model, thermal activation model, and small polaron hopping model. Optical measurements demonstrate that the SCHO powders have a direct optical bandgap of 2.25 eV in the visible light window. Having both high TC and a direct optical bandgap (2.25 eV) makes SCHO oxides attractive for use in advanced spintronic devices and solar cells. [ABSTRACT FROM AUTHOR]

The magnetic anisotropy of strontium ferrite (SF)/PA12 filament, a popular hard magnetic ferrimagnetic composites that is used for 3D-printing of permanent magnets, is studied by vibrating sample magnetometry. The studied filaments have a composition of SF/PA-12 thermoplastic composite with a 40% wt. ratio of SF. SF particles are non-spherical platelets with an average diameter of 1.3 um and a diameter to thickness ratio of 3. Filaments are produced by a twin-screw extruder and have a diameter of 1.5 mm. SEM images show that the SF particles are homogeneously distributed through the filament. VSM measurements on different parts of the filaments show that the outer part of the cylindrical filament has a higher anisotropy, and the core is mostly isotropic. This conclusion is consistent with computational work by others which suggest that particle alignment predominantly takes place near the walls of the extruder die where shear flow is maximum. Additional hysteresis curve measurement of the outer cylindrical part of the filament parallel to the r and ϕ directions indicates that the squareness of the hysteresis curve (S) is larger in the r-direction. This indicates that the outer surface of the filament has a strong easy axis in the r-direction. We conclude that the SF platelets line up parallel to the walls of the extrusion die. [ABSTRACT FROM AUTHOR]

The accelerating use of organic dyes in various industries has led to a surge in water pollution, especially from non-biodegradable dye effluents discharged into water resources. This study addresses the critical issue of catalyzing the reduction of two prevalent dyes, methylene blue (MB) and rhodamine-B (RhB), using a multiwalled carbon nanotube-cobalt ferrite (MWCNT-CF) nanocomposite. The synthesized nanocomposite demonstrates exceptional catalytic activity, stability, and recyclability. Conventional methods for treating dye-containing wastewater often prove expensive. This study explores the efficacy of catalytic reduction, a relatively fast process facilitated by semiconductor nanoparticles. Structural analyses using X-ray diffraction and high-resolution transmission electron microscopy (HRTEM) confirm the formation of the nanocomposite, revealing unsaturated surface bonds and chains conducive to adsorption. The nanocomposite exhibits a remarkable reduction in both dyes, with easy recyclability for multiple cycles. Magnetization studies confirm the ferrimagnetic nature of the nanocomposite, facilitating its efficient separation from the reaction mixture using a magnet. The study delves into the kinetics of the catalytic reduction following pseudo-first-order kinetics. The surface modifications of the nanocomposite, as revealed by TEM, contribute to enhanced adsorption and catalytic efficiency. Notably, the MWCNT-CF nanocomposite demonstrates negligible loss of catalytic activity during recycling, highlighting its potential for cost-effective and sustainable applications in dye reduction across various industries. [ABSTRACT FROM AUTHOR]

Temperature-dependent magnetization of core-shell and alloy nanoparticles of cobalt (Co)/nickel (Ni) is investigated within the context of the classical spin Hamiltonian and Monte Carlo simulations. The results of our study indicate that the average temperature-dependent magnetization and magnetic-ordering temperature have a significant influence from variations in the core-shell ratio and chemical order in core-shell nanoparticles. Also, the alloy fraction of Co(Ni) strongly influences the magnetic ordering temperature of the nanoparticles. It is noticed that in alloy nanoparticles, the rise of the magnetic ordering temperature with the increase in Co proportion is linear. However, the same is not true for core-shell nanoparticles where the magnetic-ordering temperature deviates from the straight line fit of alloy T c . It is ascertained that core-shell Co@Ni and Ni@Co nanoparticles sustain higher temperatures in their ferromagnetic state. In the ferrimagnetic nanoparticles, there is a reduction in the saturation magnetization and a display of compensation behavior. [ABSTRACT FROM AUTHOR]

The effect of temperature on electrochemical properties of Ni82.3Cr7Fe3Si4.5B3.2 glassy alloy in different acid proticity has been investigated utilizing AC and DC methods. Firstly, the handling of experimental data on the temperature dependence of charge transfer resistance, as well as corrosion current density permits us to determine the values of classical Arrhenius parameters as well as the thermodynamic ones considered approximately independent of temperature. This leads us to deduce a global interpretation on the phenomenon of corrosion and polarization. Secondly, the deviation to the linearity of the Arrhenius behavior and the real dependence on temperature of the thermodynamic parameters, permit us to clearly quantify the effect of the acid proticity and define, for the first time, the concept of current Arrhenius parameters and the current thermodynamic ones, as well as the modeling of the enthalpy–enthalpy compensation. Moreover, the effect of temperature can be investigated using the Vogel–Fulcher–Tammann model to reveal that the corresponding Vogel temperature has an interesting physical meaning. [ABSTRACT FROM AUTHOR]

We propose here an experimental method to determine the magnetization compensation temperature of ferrimagnets. Our method utilizes the first-order derivative of the spontaneous net magnetization with respect to the temperature and then analyzes the results within the context of the Bloch's law of ferrimagnetic materials. This method enables us to extrapolate the compensation temperatures, even when they exceed the measurement limit. Consequently, a wide range of compensation temperatures can be determined using a single experimental setup. The present method provides a versatile tool for analyzing huge compensation temperature in the emerging field of ferrimagnetic and antiferromagnetic spintronics. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs), which are powered by Maxwell's displacement current, have a wide range of applications, including energy harvesting and self-powered sensors. However, very little attention has been paid to the effect of the ferromagnetic medium on TENG displacement current. Herein, flexible ferrimagnetic poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF–HFP))/nickel ferrite (NiFe 2 O 4) fiber composite film based TENGs were fabricated and their performances were analysed. Highly crystalline, ferrimagnetic NiFe 2 O 4 nanofibers with high aspect ratio were prepared using electrospinning technique by systematic optimization of spinning parameters. Thereafter, the fibers were reinforced into the polymeric matrix to improve the β–phase and dielectric constant which in turn significantly enhanced the TENG performance. The β–phase enhancement in the composite films was confirmed by XRD and FTIR analysis; 77 % of the β–phase was achieved with the incorporation of NiFe 2 O 4 fiber. Morphological features were examined using SEM and AFM, which revealed more β–phase spherulite formation in the composite films. A notable increase in the dielectric properties was evidenced with the addition of NiFe 2 O 4 fibers and a maximum dielectric constant of∼26 was attained at 100 Hz. The TENG was developed using P(VDF-HFP)/NiFe 2 O 4 and nylon which generated an output voltage (V pp) and current (I pp) values of 584 V and 25 μA, respectively. Furthermore, the performance of TENG under an external magnetic field was examined, and a notable improvement in performance was observed, paving the way for the application of NiFe 2 O 4 fibers in hybrid energy harvesters and self-powered sensors. [ABSTRACT FROM AUTHOR]

Soft ferrimagnetic spinel lithium based oxides were prepared with additives like V2O5 and Na2SiO3 and sintered with the efficient microwave sintering technique. Tetravalent metal ions substituents like Mn+4, Ti+4 were used to enhance the important properties like D. C. resistivity, saturation magnetization, permeability, hysteresis and dielectric behavior. The ferrites were sintered at different sintering temperatures viz., 900, 950 and 1000 °C for 10 min by microwave technique and by conventional technique at 1050 °C for 4h. X-ray diffraction (XRD) studied the structural behavior which confirmed the spinel characteristics, Scanning electron microscopy (SEM) and EDAX revealed the microstructural and elemental compositions respectively of the ferrites. The use of additives and the microwave sintering significantly influencing the microstructural behavior and subsequently on the electromagnetic properties could be observed. Studies of initial permeability and initial permeability loss found to remain nearly constant with change in frequency until at certain frequency they showed resonance behavior. The resonance frequency's dependence on the microstructures of the ferrites could be observed. Temperature dependence behavior of the dielectric parameters and the B-H loop traced from torroidal samples of the ferrites were studied. [ABSTRACT FROM AUTHOR]

Nonreciprocal devices, including optical isolators, phase shifters, and amplifiers, are pivotal for advanced optical systems. However, exploiting natural materials is challenging due to their weak magneto‐optical (MO) effects, requiring substantial thickness to construct effective optical devices. In this study, it is demonstrated that subwavelength metasurfaces supporting bound states in the continuum (BICs) and made of conventional ferrimagnetic material can exhibit strong nonreciprocity in the Faraday configuration and near‐unity magnetic circular dichroism (MCD). These metasurfaces enhance the MO effect by 3–4 orders of magnitude compared to a continuous film of the same material. This significant enhancement is achieved by leveraging Huygens' condition in the metasurface whose structural units support paired electric and magnetic dipole resonances. The multi‐mode temporal coupled mode theory (CMT) is developed for the observed enhancement of the MO effect, and the findings with the full‐wave simulations are confirmed. [ABSTRACT FROM AUTHOR]