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• Perpendicular magnetic anisotropy [Pt/Co/Pt] multilayers grown on RuO 2 (1 0 0) • Perpendicular effective magnetic field measurements in [0 1 0] and [0 0 1] direction. • Tunable current-induced magnetization switching polarity. Current-induced perpendicular magnetization switching holds great potential for high-density magnetic storage technology. We report the growth of perpendicularly magnetized [Pt/Co/Pt] multilayers on a collinear altermagnet RuO 2 (1 0 0) thin films. The current-induced effective magnetic field was determined through anomalous Hall effect loop measurements with current applied along the [0 1 0] or [0 0 1] direction of RuO 2 (1 0 0). Magnetization switching was successfully achieved with the assistance of an in-plane magnetic field. Furthermore, by adjusting the nominal top Pt thickness of the [Pt/Co/Pt] multilayers, we could change the polarity of the current-induced magnetization switching, demonstrating an effective manipulation of spin polarization direction in RuO 2 /[Pt/Co/Pt]. These results provide a practical approach to the development of perpendicular magnetic devices based on RuO 2 and have advanced the study of spin-splitting altermagnets. [ABSTRACT FROM AUTHOR]

• Enhance the electronic and magnetic attributes of B 4 C 3 by introducing 4d TMs. • The assessment of stability for the pristine B 4 C 3 material. • Single TMs and 2TMs adsorbed B 4 C 3 demonstrate different characteristics. • The charge distribution has been assessed using Hirshfeld charge analysis. We conducted a systematic investigation of B 4 C 3 adsorbed with 4d-transition metals (4d-TMs), including Tc, Cd, Mo, Nb, Rh, Ru, and Ag, using first principles. This study involved an evaluation of structural, electronic, and magnetic properties. When single atom adsorption was adsorbed to B 4 C 3 using elements such as Tc, Nb, Rh, Ru, and Ag, it demonstrated characteristics of a diluted magnetic semiconductor (DMS), manifesting magnetic moments. Conversely, Cd, Mo, and Pd exhibited behavior consistent with non-magnetic semiconductors. Ferromagnetic (FM) and antiferromagnetic (AFM) arrangements were formed through the adsorption of 2TM atoms on B 4 C 3. In the FM setup, Ru and Nb uphold their roles as DMS. Interestingly, Tc and Rh exhibit half-metal behavior in this configuration, displaying their potential utility in spintronics applications. In the AFM configuration, Tc displayed half-metallic behavior, while the other metals maintained the same characteristics observed in the case of single TM adsorption. The reactivity of Nb-B 4 C 3 is notably high owing to its low work function, whereas Cd-B 4 C 3 is observed to be less reactive. AFM coupling is favorable in the 2Nb-, 2Rh-, and 2Ru-B 4 C 3 systems, while 2Tc-B 4 C 3 displays FM coupling. Transition metals belonging to the 4d series hold the potential to enhance the properties of B 4 C 3 , including its half-metallic, metallic, and semiconductor characteristics. These findings suggest the potential use of 4D transition metals adsorbed on B 4 C 3 as a prospective material for spintronics and magnetic storage applications in the future. [ABSTRACT FROM AUTHOR]

• The strong dependence of the magnetic properties of Mn nanowires on the step-edge geometry of the vicinal gold surfaces Au(3 3 2) and Au(3 2 2) was found. • Revealed the emergence of two exchange mechanisms (direct and indirect exchange) between manganese atoms, which are dominated either on Au(3 2 2) or on Au(3 3 2). • Found the different magnetic ground states for Mn nanowires on Au(3 3 2) and Au(3 2 2): antiferromagnetic ground state on Au(3 3 2) surface and ferromagnetic ground state on Au(3 2 2) surface. • Found the formation of stable magnetic oxide Mn nanowires on vicinal gold surfaces. • Found the increase of exchange interaction in oxide Mn nanowire compared to pure Mn nanowire due to strong interaction between Mn and O atoms. The development of quantum computing or magnetic storage systems requires the search for magnetic nanostructures with multiple magnetic configurations with controllable quantum spin states. The study of the magnetic properties of metal oxide nanowires is of particular importance for the development of these technological implementations. The present work is devoted to an ab initio study of the magnetic properties of Mn and Mn oxide (MnO) nanowires on vicinal Au surfaces with different step edge geometries. The existence of ferromagnetic and antiferromagnetic configurations of Mn and MnO nanowires on vicinal Au surfaces was found. The effect of oxidations and surface geometry on the appearance of ferromagnetic or antiferromagnetic properties of the nanowire was revealed. The ground state of pure Mn nanowires was shown to be dependent on the surface structure. At the same time, the ground state of oxide Mn nanowires is antiferromagnetic on all studied vicinal surfaces and did not depend on the surface structure. We observed an increase in the exchange interaction energy in nanowires under surface oxidation. The exchange interaction between manganese atoms in MnO nanowires is much stronger than in pure Mn nanowires. [ABSTRACT FROM AUTHOR]

Abstract Magnetization switching by injected spin-polarized current or applied field pulses is considered for perpendicular magnetic nanosystems with uniaxial symmetry and subject to thermal fluctuations. Such systems can model both perpendicular spin-transfer-torque magnetic random access memories and magnetic grains for state-of-the-art perpendicular recording. It is shown that, in the limit of high energy barriers and large current/field amplitudes, the probability and cumulative distribution functions of switching times can be analytically computed as function of material, geometrical parameters and thermal noise level. The theoretical predictions are confirmed by macrospin and full micromagnetic simulations. By using the derived formulas, it is shown that analysis of Write-Error Rates (WERs) at typical levels of reliability required by magnetic recording technology can be easily performed. [ABSTRACT FROM AUTHOR]

Abstract Topological spin textures, such as magnetic skyrmions observed in certain chiral magnets, are one of the most interesting ordered phases in condensed matter. A skyrmion is a swirling spin structure carrying a topological quantum number. Skyrmions were first observed in MnSi, in 2009, and later observed in Cu 2 OSeO 3 , a chiral antiferromagnet with T N = 58 K that can be synthesized by reacting CuO and SeO 2 at 600 ° C. Using a transport agent (typically ammonium chloride) in a chemical vapour transport reaction, single crystals can be grown. As skyrmion lattices may find use in nanotechnological devices, such as data storage systems and in other applications, the magnetic properties of nano-sized compounds deserve to be investigated. The following work presents the synthesis and magnetic studies of the nanocrystalline form of Cu 2 OSeO 3 obtained by an alternative route, thermal decomposition of CuSeO 3 ·2 H 2 O. This procedure afforded nanostructured samples of reasonable purity (> 95 %). Structural, morphological and magnetic characterization of these samples are reported, aiming to study the effect of nanostructuring on the magnetic phases, in particular the presence and stability of the skyrmionic lattice. [ABSTRACT FROM AUTHOR]

Abstract Skyrmions are nanoscale and topologically protected objects, which are promising candidates for information carriers of magnetic storage devices. To this end, the rapid creation and manipulation of a single skyrmion is required. In this work, a spin-valve device with a single-skyrmion reference layer is considered. Using micromagnetic simulations, we find that a skyrmion is likely to nucleate in the free layer as a picosecond current pulse is applied. In addition, we also demonstrate that the skyrmion in the free layer can be reversed by injecting an alternating current. It is promising that such a study can benefit the development of skyrmion-based storage devices. [ABSTRACT FROM AUTHOR]

Graphical abstract Doping 5d atom could manipulate the magnetic and electronic properties in blue phosphorene, which could be a next-generation candidate of potential spintronics material. Highlights • The properties of 5d transition metal doped blue phosphorene are systematically investigated. • The W- and Os-doped blue phosphorene show the dilute magnetic semiconductor properties. • The Hf-, Ta-, Re- and Hg-doped systems exhibit half-metallic state. • The Re-doped system shows the largest magnetocrystalline anisotropy energy (MAE) of −30.25 meV. Abstract The structural, energetic, electronic and magnetic properties of 5d series transition metal atom substitutionally doped blue phosphorene are systematically investigated. It is found that the spin polarized state can be induced in the doped blue phosphorene, except for the Ir- and Pt-doped systems. Spin density and Bader charge analyses indicate that the magnetic moments of the 5d-doped systems mainly originate from the 5d electrons of the TMs, except for the Au- and Hg-doped systems. The electronic structure calculations indicate that the Ir- and Pt-doped systems show semiconducting and metallic behaviors, respectively. The W- and Os-doped systems show dilute magnetic semiconductor properties and the Au-doped system shows metallic behavior. Especially, the Hf-, Ta-, Re- and Hg-doped systems exhibit half-metallic state, which can act as ideal spin electronic injection source of semiconductor. Moreover, the Re-doped system shows the largest magnetocrystalline anisotropy energy (MAE) of −30.25 meV in the present studied systems, and its MAE could be enhanced to −42.97 meV by applying an electric field of up to 1.0 V/Å. Our study demonstrates that the 5d doping could provide various potential applications in spintronics and magnetic storage devices for blue phosphorene. [ABSTRACT FROM AUTHOR]

Skyrmions are emerging topological spin structures that are potentially revolutionary for future data storage and spintronics applications. The existence and stability of skyrmions in magnetic materials is usually associated to the presence of the Dzyaloshinskii-Moriya interaction (DMI) in bulk magnets or in magnetic thin films lacking inversion symmetry. While some methods have already been proposed to generate isolated skyrmions in thin films with DMI, a thorough study of the conditions under which the skyrmions will remain stable in order to be manipulated in an integrated spintronic device are still an open problem. The stability of such structures is believed to be a result of ideal combinations of perpendicular magnetic anisotropy (PMA), DMI and the interplay between geometry and magnetostatics. In the present work we show some micromagnetic results supporting previous experimental observations of magnetic skyrmions in spin-valve stacks with a wide range of DMI values. Using micromagnetic simulations of cobalt-based disks, we obtain the magnetic ground state configuration for several values of PMA, DMI and geometric parameters. Skyrmion numbers, corresponding to the topological charge, are calculated in all cases and confirm the occurrence of isolated, stable, axially symmetric skyrmions for several combinations of DMI and anisotropy constant. The stability of the skyrmions in disks is then investigated under magnetic field and spin-polarized current, in finite temperature, highlighting the limits of applicability of these spin textures in spintronic devices. [ABSTRACT FROM AUTHOR]

The metal magnetic memory signals were measured during dynamic tension tests on the surfaces of the cladding coatings by plasma transferred arc (PTA) welding and the 0.45% C steel. Results showed that the slope of the normal component H p ( y ) of magnetic signal and the average value of the tangential component H p ( x ) reflect the magnetization of the specimens. The signals increased sharply in the few initial cycles; and then fluctuated around a constant value during fatigue process until fracture. For the PTA cladding coating, the slope of H p ( y ) was steeper and the average of H p ( x ) was smaller, compared with the 0.45% C steel. The hysteresis curves of cladding layer, bonding layer and substrate were measured by vibrating sample magnetometer testing, and then saturation magnetization, initial susceptibility and coercivity were further calculated. The stress-magnetization curves were also plotted based on the J-A model, which showed that the PTA cladding coating has smaller remanence and coercivity compared with the 0.45% C steel. The microstructures of cladding coating confirmed that the dendritic structure and second-phase of alloy hinder the magnetic domain motion, which was the main factor influencing the variation of magnetic signal during the fatigue tests. [ABSTRACT FROM AUTHOR]

[Display omitted] • Enrich the electronic and magnetic properties of Sb by adsorption of 4d TMs (Ag, Cd) and 5d TMs (Ir, Pt, Au, Hg). • The stability analysis of pristine antimonene. • Single TMs and 2TMs adsorbed Sb exhibit metallic and semiconducting features that induced magnetic moments. • The analysis of Charge density difference by using NBO calculation. For spintronic devices, the adsorption of transition metal (TM) atoms may provide two-dimensional (2D) materials with enhanced electrical and magnetic characteristics. Herein, the stability, electronic, and magnetic properties of 4d (Ag, Cd) and 5d (Ir, Pt, Au, Hg) TM adsorbed mono-layer antimonene (Sb) are investigated thoroughly using first-principles calculations. We find out the stability and suitability of the material by using different parameters like relative formation energy, thermal stability, and phonon dispersion curve. The adsorption energies suggest that the most favorable position of adsorption is the hollow (H) site where the ground state energy is lowest. In the case of Ir, and Au adsorbed Sb, the metallic and magnetic behavior is observed due to the change of spin-up and down. Adsorption of Ag also reveals metallic behavior but there is symmetry in high and low spin and shows non-magnetic results. Interestingly, the spin-polarized semiconducting state appears in Cd, Pt, and Hg adsorbed Sb and shows non-magnetic semiconductor behavior. Our study reveals that the TMs adsorbed Sb can be used in potential applications like spintronics, magnetic storage devices, optoelectronics, and Nanoelectronics applications. [ABSTRACT FROM AUTHOR]

• Composites Bi 5 Ti 3 FeO 15 /Bi 2 Fe 4 O 9 are prepared via the sol–gel modified method. • Maximum value of MD% is obtained for the x = 0.2 sample, which is correlated with the maximum change in Fe-O bond length in the composite. • Inverse Dzyalonskii-Moriya interaction possibly causes the enhanced MD effect in the composites. • The maximum coupling coefficient γ (6.79 emu−2. g2) is obtained for x = 0.4 composite. • The intrinsic nature of MD coupling is addressed from the magnetoimpedance, Cole-Cole plot, and magnetoconductance analysis. The physical properties of the Aurivillius Bi 5 Ti 3 FeO 15 compound are enhanced by adding the magnetic BFO compound. The magnetic, magnetodielectric (MD), and magnetoimpedance (MI) properties of Bi 5 Ti 3 FeO 15 /Bi 2 Fe 4 O 9 composites are investigated. The samples are prepared by the sol–gel-modified method, and the Rietveld refinement verifies the diphasic nature of the composites. The Raman spectra demonstrate the shifting of the vibrational modes due to adding the BFO phase, which is associated with the BO 6 (B = Fe/Ti) octahedral. The maximum shift in Raman modes and bond length of Fe-O is noticed for the x = 0.2 composite. Room temperature magnetization data reveals the highest value of M s and M r is found for x = 0.2 composite, which is caused by the interaction among the AFM/FM magnetic ordering. The frequency-dependent MD shows the maximum MD% strength of ∼0.55 % for x = 0.1 and minimum magnetoloss (ML)% of ∼0.08 % for x = 0.3 composites. Field variation of MD data shows ∼30 times enhancement of MD% and ∼7 times reduction of the ML% for x = 0.2 sample as compared to the pure sample. The enhanced MD effect is due to the non-collinear ordering of Fe spins in the BFO sample, which results in the possible inverse Dzyalonskii-Moriya interaction in the composites. Additionally, the Ginzburg-Landau approach confirms that the maximum coupling coefficient γ (6.79 emu−2. g2) is observed for x = 0.4 of the BFO sample. The field-dependent capacitive MI and Cole-Cole plot analysis reveals the capacitive origin behind the MD effect. The non-linear variance of magnetoconductance in the pure sample (x = 0.0) is attributed to the maximum ML%. Hence, the enhanced MD coupling with capacitive MI properties is a great advantage for designing magnetic sensors and storage devices. [ABSTRACT FROM AUTHOR]

• Vacuum and air sintered Bi-doped YIG have been prepared along with pure YIG using the sol–gel auto-combustion method. • The dielectric properties have enriched, and tangent loss has decreased for vacuum sintered Bi-doped YIG compared to YIG and air sintered Bi-doped YIG ceramics. • It also shows the better dielectric response with applied magnetic field so that it can be used for field sensing applications along with passive microwave devices. • We have observed large magneto-electric effect at the room temperature for all the ceramic samples and YBIG-V ceramic is maximum among them. • We have correlated the enhanced dielectric characteristics to the magnetic properties obtained through VSM measurements and attribute to the reduction in deficit oxygen states or Fe2+ concentration due to the vacuum sintering process which has also been confirmed through XPS studies. Yttrium iron garnet (YIG; Y 3 Fe 5 O 12) is an important material in the field of electronics because of its unique magnetic properties. This makes it ideal for use in devices such as microwave filters, amplifiers, sensors, and even magnetic storage devices. It is also used in spintronics, which is the study of the spin of electrons and how it can be manipulated for storage and computation. Additionally, it is highly stable and has low losses when exposed to electromagnetic fields, making it useful in applications such as controlling electric properties with magnetic fields or vice-versa, and magnetic resonance imaging (MRI). Herein, we have prepared YIG and Bi-doped YIG (Bi: YIG: Y 2 Bi 1 Fe 5 O 12) nanoparticles (NPs) using the sol–gel auto-combustion method. The obtained garnet powders were sintered at 950 °C both in an air and vacuum environment. We have explored the structural, electrical, optical, magnetic, and magneto-electric (ME) properties of Bi-doped YIG sintered in a vacuum (YBIG-V) and compared it with YIG and Bi-doped YIG sintered in the air (YBIG-A). We found the enhancement in dielectric response, magnetic properties, and the reduction in leakage current for the YBIG-V ceramics than for YBIG-A, YIG ceramics. We have studied the magneto-electric (ME) coupling at room temperature and found that YBIG-V ceramics show the better coupling strength with a maximum coupling coefficient, α ME of 354.3 mV/cm-Oe. The dielectric response of these samples significantly varies with the applied magnetic field, which will be positive in Bi-doped YIG ceramics and negative in pure YIG ceramics. Compared to YBIG-A, YBIG-V samples have better variation in dielectric response with the magnetic field, due to which they may be utilized for magnetic field sensing applications. We also observed that the resonance frequency varies with the applied magnetic field, which may be another parameter for field sensing applications. We attribute the enhancement of these properties in YBIG-V sample to the reduction in the average oxygen valency which is 1.63 for YBIG-A and 1.58 for YBIG-V. These values have been determined with the help of X-ray photoelectron emission spectroscopy data. [ABSTRACT FROM AUTHOR]

• CoO/Co magnetic nanocaps were fabricated by depositing Co films on curved nanosphere (PS). • Films also deposited on bare Si substrate during the same deposition cycle. • The magnetic nanocap formation was confirmed from magnetic measurements. • The magnetic observations were further supported by structural and morphological observations. • The studied film and the reference film were grown in polycrystalline manner while their roughnesses were quite different as observed from XRD and XRR techniques respectively. The importance and applications of nanoscale magnetic storage devices has been of current interest owing to the extensive research interest in magnetic nanocaps. Continuing their research trend, we have attempted to synthesize and characterize an important isolated magnetic nanocaps system constituting Co and its oxide. CoO/Co thin films were deposited onto self-assembled arrays of polystyrene (PS) nanospheres (∼600 nm diameter) under ultra-high vacuum environment using electron beam evaporation technique. The magnetic and structural properties of these nanostructures were then compared with those of simultaneously deposited films on bare Si substrate (referred to as reference film). The studied film and the reference film were grown in polycrystalline manner as observed from X-ray diffraction measurements while their roughnesses as observed from X- ray reflectivity were quite different. X- ray reflectivity showed that for the reference films well defined Kiessig oscillations appeared suggesting low roughness in the deposited films, while the films on PS followed the curvature of underlying nanospheres and thus have very high roughness resulting in the disappearance of Kiessig oscillations. Magnetic measurements exhibited a drastically high coercivity when the substrate was changed from flat (Si) to curved one (PS). As the film thickness was increased, the coercivity first showed a slight decrement (4.92 kA/m) and beyond 40 nm film thickness, it showed some enhancement (14.2 kA/m). The exchange bias measurements also showed interesting results with variation in film thickness. Co 10 nm film deposited on PS showed negative exchange bias of −127 kA/m which decreased to −26 kA/m in 100 nm film. The overall results were explained by correlating the magnetic and microstructural properties of the thin films as a function of thickness. [ABSTRACT FROM AUTHOR]

• In-depth investigation of Magnetization reversal in the presence of interfacial Dzyloshinskii-Moriya interaction (IDMI) and the in-plane bias field (H) on square, circular and triangular nanodots. • The energy barrier is significantly reduced in all nanodots by increasing the strength of the IDMI and H. • The lowering of the energy barrier for the magnetization reversal is intricately related to the symmetry associated with the shape of the nanodots. • Disentangle the spin canting induced by the IDMI from the geometrical induced one. Thorough understanding of magnetization reversal process in perpendicularly magnetized nanostructures of different shapes in the presence of anti-symmetric exchange interaction is crucial in designing energy efficient magnetic storage devices. Here, we investigate the effect of interfacial Dzyaloshinskii-Moriya interaction (IDMI) and in-plane bias field (µ 0 H) on the magnetization reversal mechanism in perpendicularly magnetized square, circular and triangular nanodot of side length (diameter) 128 nm and thickness 1 nm using micromagnetic simulation Mumax3. Our results indicate a monotonic reduction in the coercive field with increase in the strength of IDMI and the nucleation of the reversal is observed at the edge of the nanodot irrespective of the shape. Additionally, the application of bias field pins the nucleation centre at the far edge of the dots and further lowers the energy barrier for the magnetization reversal with the extent of lowering related to the symmetry of the shape. Detailed analysis of energy profile reveals that due to the lateral asymmetry of the triangular nanodot (large spin canting), the total energy value is smaller for it at small magnitude of D (≤2 mJ/m2) and µ 0 H (≤100 mT) thereby making it preferred for energy efficient magnetization reversal in comparison to other two shapes. However, at sufficiently large magnitude of D (>2 mJ/m2) and µ 0 H (>100 mT), due to the laterally symmetric sides of the square (small spin canting), remarkable reduction of the energy barrier for the magnetization reversal is noticed. These findings indicate that the effect of D and µ 0 H in lowering the energy barrier for the magnetization reversal is intricately related to the symmetry associated with the shape of the nanodots. We thus believe that these results provide useful insight into the role of the shape of the nanoelement in designing spintronics devices where energy efficient magnetization reversal is required. [ABSTRACT FROM AUTHOR]

[Display omitted] • Role of Sm3+-ion doping on physical properties of BiFeO 3. • Sm-doped BiFeO 3 samples synthesized using solid-state reaction route. • With the increase of Sm3+ content, T N gradually decreased. • Sm-doped BiFeO 3 samples exhibit ferromagnetic and antiferromagnetic behaviors. We report the role of novel samarium (Sm3+) doping on the structural, thermal, magnetic, and ferroelectric properties of BiFeO 3. Polycrystalline Sm-doped BiFeO 3 samples were synthesized using a conventional solid-state reaction route. Bi 1- x Sm x FeO 3 (x = 0.02–0.08) samples crystallize in rhombohedral structure (R 3 c). With the increase of Sm3+ content, the decrease in crystal size is attributed to the change in lattice parameters, since the ionic radius of Sm3+ (0.95 Å) is smaller than that of Bi+3 (1.03 Å). A clear magnetic transition temperature (T N) peak was obtained by DSC measurements. With the increase of Sm3+ content, the peak temperature gradually decreased. Sm-doped BiFeO 3 samples exhibit ferromagnetic and antiferromagnetic behaviors. Magnetism is strongly influenced by the substitution of Sm3+ ions in BiFeO 3 , and thus the magnetism of the synthesized samples is greatly changed compared to that of pure BiFeO 3. Bi 1- x Sm x FeO 3 (x = 0.02–0.06) samples have weak pointed hysteresis loops. While the BSFO-0.08 sample exhibit unsaturated rounded hysteresis loops possibly due to the large electrical leakage. Overall, we observed enhanced magnetic and ferroelectric properties by varying the Sm3+ content in BiFeO 3. Therefore, the Sm3+ doping in BiFeO 3 makes it a very prospective material for applications in spintronic devices, data storage devices, and sensors. [ABSTRACT FROM AUTHOR]

• Heusler-type Ni 44 Co 6 Mn 37 In 13 alloy has been successfully fabricated by arc melting. • Microstructure measurements verify the 'kinetic arrest' of martensitic transformation. • Large magneto-functional properties are achieved around room temperature. • Large magnetoresistance benefited from the high sensitivity of transformation to the field. • Proper increase in T C of austenite would yield excellent magneto-functional properties. NiMn-based Heusler alloys are promising materials in the multi-functional applications due to their ample magneto-responsive effects across martensitic transformation, such as magnetocaloric effect, magnetostriction and magnetoresistance. In this work, the evolution of microstructure, large magnetocaloric and magnetoresistance effects during martensitic transformation are systematically studied in a Ni 44 Co 6 Mn 37 In 13 alloy. Magnetic and caloric measurements verify that the martensite in weak magnetic state would gradually transform to be ferromagnetic austenite upon heating. The temperature dependence of microstructure observed in an in-situ optical microscopy unambiguously verify the 'kinetic arrest' of martensitic transformation. Most importantly, due to the high sensitivity of transformation to the magnetic field, large magnetocaloric and magnetoresistance effects near room temperature are obtained, including magnetic entropy changes of 8.4 Jkg-1K−1, effective refrigerant capacity of 181 Jkg−1 and magnetoresistance change of 75 % under the field change of Δ μ 0 H = 0–5 T, making the studied sample promising for room temperature magnetic refrigeration and magnetic storage. [ABSTRACT FROM AUTHOR]

Hard disk drives have become the most commonly used mass storage devices because of their low cost and high storage capacity. However, the current perpendicular magnetic recording technology is reaching the physical limit for its areal density capability (ADC) due to superparamagnetism. To accommodate the rapid increase in the volume of digital data produced globally, heat-assisted magnetic recording (HAMR) has been introduced as a next-generation recording technology. In HAMR, a laser locally heats the media to reduce the coercivity, with the information recorded during the cooling process. To investigate the high-temperature magnetization dynamics that occur during this form of recording, computational micromagnetics is a useful tool. This article provides a brief review of micromagnetic modeling for HAMR and summarizes simulation-based studies on HAMR media. A review of these simulation results can serve as a guideline for the prediction of the ADC limit of HAMR. • The continued dominance of cloud storage by magnetic recording requires ever increasing user areal densities, currently at about 1 Tbit/in2. • The recent commercial introduction of Heat Assisted Magnetic Recording (HAMR), although exciting, has so far increased densities little. • To investigate and improve the high-temperature magnetization dynamics that occur during this form of recording, computational micromagnetics is a useful tool. • This article provides a brief review of micromagnetic modeling for HAMR and summarizes simulation-based studies on HAMR media. • A review of these simulation results can serve as a guideline for the prediction of the ADC limit of HAMR. [ABSTRACT FROM AUTHOR]

Nanoscience and its associated nanotechnology started several decades ago to discover and harness properties and behavior of materials that occur due to lowering their dimensionality. Nanomagnetism, which is the branch of nanoscience to investigate magnetic properties of materials down to fundamental length and time scales led to the discovery of a plethora of novel nanoscale spin phenomena and has further laid the groundwork for spintronics, which has become the primary enabler for the most advanced information technologies, including magnetic storage and sensor devices. So far, low-dimensional magnetic systems have been confined to zero (quantum dots), one (nanowires), and two (thin films) dimensions, however, recently research with artificially designed three-dimensional magnetic systems is emerging as it opens the path to novel scientifically exciting phenomena with enormous technological potential to advance spintronics further towards ultrasmall, ultrafast and most importantly low-power electronics. These three-dimensional structures harness the scientific achievements from traditional nanomagnetism, but expand them in a tailored way into the third dimension. Local curvature, particular when defined in a rather broad sense, including geometrical curvature adds to a traditional 2D film a third dimension and proximity effects drawing upon the 3D environment are among the design principles for those 3D magnetic systems. This critical focus article reviews briefly the current state-of-the-art of the emerging research topic with 3D nanomagnetic materials, and describes some of the challenges that the research community needs to address in terms of synthesis and fabrication, theory and modelling, as well as characterization and validation to ultimately bring to bear potential applications with 3D nanomagnetic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Structural parameters of nano cobalt ferrite (CFO) alter upon doping and sintering. • Substitution of large ions in nano cobalt ferrite affects vibrational frequencies. • Magnetic parameters dependent on particle size, temperature and colinearity. • Conductivity by hopping of charge, shows large dielectric constant at low frequency. • Influence of temperature on dielectric and magnetic properties emphasized. Instruments and devices based on magnetic materials have become necessity and indispensable for human being in the modern culture. The applications of these material are growing exponentially ever since the first magnetic mineral known to humanity, loadstone magnetite, Fe 3 O 4. Ferrites based materials take the lion share in magnetic materials. Among the spinel ferrites, cobalt ferrite (CFO) has got much attention of various research groups during the last decades due to its applications in household items to high density data storage and magnetic resonance imaging (MRI) contrast agents to camouflaging military installations and stealth applications. The CFO is hard magnetic material with high anisotropy constant and Curie temperature yet versatile due to its moderate saturation magnetization with flexible dielectric and transport properties. Many elements of periodic table with variable amount can be incorporated in cobalt ferrite spinel matrix at both tetrahedral and octahedral sites by a wide variety of dry and wet chemical synthesis routes to tailor physical properties for various applications. This systematic review focuses types of ferrites, structure, and room-temperature (RT) and Low-temperature magnetic dielectric properties of pristine and metal doped CFO. This article gives an overview of X-ray diffraction (XRD) and effect of calcination temperature, Fourier transform infrared spectroscopy (FTIR) techniques. Room temperature (RT) and Low-temperature Field cooled (FC) and zero field cooled (ZFC) magnetic properties, dielectric Properties, ac conductivity and impedance spectroscopy of pristine and doped CFO. Furthermore, the impact of some group II and transition metal doping on various properties of CFO and their application were reviewed. The final section deals with doping of CFO by Rare-earth (RE) (La, Ce, Sm, Gd, Dy and Er) reviewing their structural, magnetic, and dielectric properties and applications. Overall, this review article reports the structural, RT and Low temperature magnetic, dielectric properties of CFO, besides doping of CFO by transition and RE metals, highlighting the recent research on CFO Nanoparticles. [ABSTRACT FROM AUTHOR]

• Mn and Co-doping at various host sites induce significant change in magnetic behavior inducing impressive magnetic moments with unwavering dilute doping concentration. • By employing magnetic ions such as Mn, Co at various host atom sites, we ratify a significant change in magnetic behavior inducing impressive magnetic moments with unwavering dilute doping concentration. • Both Mo and W-sites and is found to have long ranged ferromagnetic ground state with Co doping. • The electronic properties modification-induced change in magnetic exchange interaction reflecting the possible emanations of magnetic orderings in novel vdW non-magnetic heterostructures. Atomically thin doped two dimensional (2D) layered materials manifest excellent magnetic features beneficial to the potential applications in spintronics. With the implementation of extensive first principles calculations, we demonstrate the MS 2 (M = Mo, W) monolayers, as well as their van der Waals (vdW) hetero-bilayers as promising candidates for the successful realization of 2D dilute magnetic semiconductors with the incorporation of Mn and Co dopants. Under various pairwise doping configurations at different host atom sites, we report the electronic properties modifications induced change in magnetic exchange interactions. The magnetic coupling among the dopant pairs can be tuned between FM and AFM orderings via suitable doping adjustments. The developed interlayer exchange coupling between the vdW layers leads to strong and long-ranged ferromagnetic interactions which unleash robust magnetic moments with stable doping configurations. Our findings address the novel magnetic behavior of the layered vdW heterostructures and may further guide the future experimental efforts for the possible applications in modern electronics and nanoscale magnetic storage devices. [ABSTRACT FROM AUTHOR]

In the recent past, current-induced magnetization reversal (CIMR) has been extensively studied on the heterostructures prepared with heavy metal (HM) and ferromagnet (FM) having spin–orbit torque (SOT). The critical current density (J c) for magnetization switching depends on the SOT efficiency. In this study, we have chosen Ta/Pt/CoFeB/Pt/Ta/CoFeB/Pt heterostructure having perpendicular magnetic anisotropy (PMA) with broken lateral symmetry and an in-plane magnetized (IMA) ferromagnetic layer on top of the Ta layer. In this heterostructure, we have utilized the SOT originated by the spin-Hall effect that arises from two materials having opposite spin Hall angles i.e. the bottom Pt and the top Ta layer. We have also introduced lateral space inversion asymmetry (SIA) that combines both damping-like and field-like field. The enhanced spin Hall angle, the stray field by IMA ferromagnetic layer, and the lateral SIA effect jointly enhances the SOT efficiency of the system to reduce the J c for CIMR. We have found that the SOT efficiency and the effective spin Hall angle of our newly designed heterostructure to be 106 Oe / 1 0 11 A/m2 and 0.23, respectively. Thus we have achieved CIMR with a lower critical current density of 8. 65 × 1 0 10 A/m2 and 3. 35 × 1 0 10 A/m2 at 0 Oe and 600 Oe field applied in-plane (IP), respectively. Due to the lower J c for CIMR our newly designed heterostructure has potential in low-power magnetic data storage applications. • SHE, stray field, and lateral space inversion asymmetry enhanced the SOT efficiency. • Enhanced SOT efficiency reduces the critical current density to switch magnetization. • Zero field switching observed for critical current density, J c = 8.65 × 1 0 10 A/m 2. • Critical current density as low as J c = 3.35 × 1 0 10 A/m 2 attained at 600 Oe. • The device has massive potential in low-power magnetic data storage applications. [ABSTRACT FROM AUTHOR]

Exchange coupled ferri-/ferromagnetic heterostructures are a possible material composition for future magnetic storage and sensor applications. In order to understand the driving mechanisms in the demagnetization process, we perform micromagnetic simulations by employing the Landau–Lifshitz–Gilbert equation. The magnetization reversal is dominated by pinning events within the amorphous ferrimagnetic layer and at the interface between the ferrimagnetic and the ferromagnetic layer. The shape of the computed magnetization reversal loop corresponds well with experimental data, if a spatial variation of the exchange coupling across the ferri-/ferromagnetic interface is assumed. [ABSTRACT FROM AUTHOR]

• Fabrication of flexible magnetoelectric (ME) P(VDF-HFP)/SrFe 12 O 19 composite films. • Inclusion of SrFe 12 O 19 nanofiber enhances the polar β-phase in P(VDF-HFP) matrix. • P(VDF-HFP)/SrFe 12 O 19 films exhibit enhanced dielectric and ferroelectric properties. • A strong strain mediated ME coupling exists in the P(VDF-HFP)/SrFe 12 O 19 films. • P(VDF-HFP)/SrFe 12 O 19 films' energy storage capacity is tuned by magnetic fields. Flexible, self-standing magnetoelectric (ME) polymer composite films were prepared using the solution casting method by reinforcing one-dimensional ferromagnetic strontium ferrite (SrFe 12 O 19) nanofibers, synthesized using the electrospinning method, into poly(vinylidene fluoride–hexafluoropropylene) (P(VDF-HFP)) matrix. The effects of loading of SrFe 12 O 19 nanofibers on the functional, structural, magnetic, dielectric, and ferroelectric properties of P(VDF-HFP) were investigated. The loading enhanced the electroactive β-phase of the films, as confirmed by XRD and FTIR analyses. The ME coupling that existed in the composite films was confirmed by the changes in ferroelectric parameters under various magnetic fields. The energy storage capacity and dielectric constant of the composite films were enhanced with the addition of SrFe 12 O 19 nanofibers, with the maximum values of 56 at 100 Hz and 1678 mJ/cm3 at 444 kV/cm, respectively, in the composite film with 20 wt% SrFe 12 O 19 nanofibers. The energy storage capacity was further enhanced and tuned by applying an external magnetic field. Thus, this work reports an innovative approach to tuning the energy storage capacity of ME polymer composite films through a magnetic field and also describes use of these films for a wide range of applications, such as energy storage and memory devices and magnetic sensors. [ABSTRACT FROM AUTHOR]

[Display omitted] • The transition metal (TM) atoms (Mn, Fe, Co) adsorbed SnX (X = S, Se, Te) monolayers (MLs) are energetically stable with the pnma space-group and show semiconducting nature with the electronic band gaps in between 0.52–1.05 eV. • Magnetic states are realized for SnX atoms in the adsorbed systems with the induced magnetic moments between −0.03 to −0.33 μ B , which indicate the antiferromagnetic alignment between TM atoms and neighboring SnX atoms. • The p -type doping is induced in the SnX MLs upon TM atoms adsorption as indicated by the calculation of charge transfer between the adsorbed TM and SnX atoms. Magnetism can be induced in two-dimensional (2D) group IV monochalcogenide monolayers (MLs) by the decoration of transition-metal (TM) atoms. The induced magnetism in the group IV monochalcogenides enhances their potentiality in 2D spintronic devices, which has attracted extensive attention nowadays. In this context, the structural, electronic, and magnetic properties of transition metal atoms (Mn, Fe, Co) adsorbed SnX (X = S, Se, Te) MLs are investigated by using first-principles calculations. The TM atoms adsorbed SnX MLs are found to be energetically stable with the pnma space-group, and show the semiconducting nature with electronic band gaps in the range of 0.52–1.05 eV revealing the negligible spin–orbit coupling effect in most of the studied systems. The asymmetry between spin majority and spin minority channels is revealed in the electronic density of states of the adsorbed systems, which is mainly contributed by the hybridization of the 3d orbitals of TM atoms with the 4p and 4s orbitals of Sn and X atoms. Magnetic states are realized for SnX atoms in the adsorbed systems with the induced magnetic moments between −0.03 to −0.33 μ B , which indicates the antiferromagnetic alignment between TM atoms and neighboring SnX atoms. Co adsorbed SnSe and Fe adsorbed SnTe MLs are found to have significant magneto-crystalline anisotropy energy values of 0.37 and 0.84 meV/TM atom, respectively, with the preferred perpendicular direction. In addition, the p -type doping is induced in the SnX MLs as indicated by the calculation of charge transfer between the adsorbed TM and SnX atoms. The results demonstrate potential applications of TM atoms adsorbed SnX MLs for spintronic and magnetic storage devices. [ABSTRACT FROM AUTHOR]

We present images of spin-wave excitations in a patterned yttrium iron garnet (YIG) thin film obtained by use of near-field microwave microscopy, which can achieve spatial resolution as high as 50 nm. Visualization of magnetic excitations is an enticing prospect for high-speed, high-density magnetic logic and storage applications, which has spurred the development of new magnetic microscopy and imaging techniques in recent years. Here we present a novel approach for local imaging of magnetic modes excited at room temperature with sub-diffraction-limited spatial resolution. This approach is based on a special atomic force microscope with broadband GHz capability for imaging the spatial distribution of dynamic magnetic excitations in patterned magnetic structures. Due to the inherent sub-wavelength, nanometer-scale spatial resolution of near-field scanning probe techniques, this approach has potential for a significant improvement in spatial resolution over optical techniques. [ABSTRACT FROM AUTHOR]

Artificial defect influence on transverse domain wall dynamics have been investigated in permalloy nanowires using micromagnetic simulation. For given defect geometry, it has been obtained that domain walls transit from transverse to vortex at depinning current. The transition provides a way to reveal the intrinsic properties of transverse and vortex domain walls. Moreover, the calculated results show that with the increase of defect width, depinning current reaches a maximum and then decreases. However, for angle dependent current, it decreases to a minimum value and then increases with angle. These results are helpful for fabricating defect geometry and have potential applications in designing magnetic storage devices. [ABSTRACT FROM AUTHOR]

• The thermal stability of DW switching in nanowires is strongly dependent on the improvement of magnetic properties and nanowire geometry. • Both domain wall types (TDW and VDW) switching be more stable against nanodevice temperature, which are good candidates for storage applications. • The device temperature influences TDW velocity; it was found that TDW velocity increases by increasing the device temperature. The domain wall (DW) random switching in planar magnetic nanowires is one of the crucial problems for storage data applications. Hence, a micromagnetic simulation was used to investigate the transverse domain wall (TDW) nucleation in the thinner and narrower nanomagnetic devices and the vortex domain wall (VDW) nucleation for the thicker and wider nanowires due to the device temperature. The TDW thermal creation was examined based on magnetic properties such as uniaxial magnetic anisotropy energy (Ku) and saturation magnetization (Ms). The thermal stability of TDW switching in nanowires is strongly dependent on the improvement of magnetic properties, whereas the TDW thermal nucleation decreases by increasing Ku or Ms. In addition, the TDW and VDW thermal creation in storage nanodevices such as nanowires could be controlled by nanowire geometry manipulation like width and thickness. Reducing the nanowire width or increasing its thickness helps both domain wall types (TDW and VDW) switching to be more stable against nanodevice temperature. TDW thermal switching was found to be stable under a device temperature of up to 500 K, which is higher than the room temperature. However, the VDW shows higher thermal stability switching reaches up to 900 k, which are good candidates for storage applications. Furthermore, the TDW dynamics in nanowires were affected by device temperature, whereas the TDW moves faster by increasing nanodevice temperature. All these findings will help to maintain the storage memory in nanodevices from failure due to device temperature. [ABSTRACT FROM AUTHOR]

• Co-precipitation method is used to grow single phase Sn 1−x Zr x O 2 ferromagnetically-like behavior Semiconductors. • XRD determine nano Crystallite nature of Sn 1−x Zr x O 2. • The synthesized samples show responses to the incident frequencies. • The ac conductivity is enhanced due to Zr doping giving significance results. • The impedance analysis shows the contribution of grains and grains boundaries. • The observed room temperature ferromagnetic-like behavior indicates potential magnetic storage applications. • The synthesized DMS nanoparticles have useful spintronic applications. The multifunctional and tunable properties of semiconductors can be achieved by intentional doping of the host lattice with appropriate impurities. In this study, the structure, ferromagnetism and dielectric response of Zr doped SnO 2 nano-crystallites, fabricated using co-precipitation technique, have been investigated. X-ray diffraction studies confirm the successful fabrication of Zr doped SnO 2 along with one minor peak belonging to SnO. The measured surface morphology shows non-uniform and denser grain distribution. The optical studies show decaying band gaps. The impedance analysis reveals grains and grain boundaries conduction exhibiting different relaxation times. The maximum grains capacitance has been observed in 4% of Zr content. Furthermore, above room temperature ferromagnetic-like behavior is observed, which is quite attractive for magnetic device applications. Hence, the studied diluted magnetic semiconductors are appealing not only for fundamental physics but also for technical applications in frequency related devices and in data processing and storage devices. [ABSTRACT FROM AUTHOR]

• We proposed a method to get a low-power-driven, unidirectional and ultrafast switching of magnetic vortex core under a continuous rotating magnetic field in a nanocavity mediated nanodisk. • The vortex core can be unidirectionally switched within 0.34, 0.47 and 0.86 ns under the excitation field with amplitude 4, 3 and 2 mT, respectively by choosing a proper value of the nanocavity's diameter and height. • Although the rotating magnetic field is applied, the amplitude of the core motion is very small, since the core is confined in the nanocavity. This is conducive to bit reading in magnetic data storage devices. Reliable unidirectional switching of magnetic vortex core driven by continuous rotating magnetic field is investigated using a permalloy nanodisk with a nanocavity inserted in the center in combination with micromagnetic simulations. It is reported that once the vortex core is confined in a nanocavity of diameter is comparable to the core size, the modes of the core motion (divergence/convergence modes) are modulated differently by the nanocavity: the threshold field amplitude required for vortex core switching is reduced for convergence mode, but not for divergence mode. We found that the confinement of the nanocavity to the core is mediated by the cavity height as well. Low-power-driven fast unidirectional switching is found to be achievable by carefully choosing the value of the nanocavity height. [ABSTRACT FROM AUTHOR]

• Double-gradient structures from Fe and Py reverse magnetization via few steps. • Double-rectangle structures start magnetization reversal with horseshoe states. • The latter allow for preparing stable quaternary magnetic storage devices. Magnetic vortices belong to the possibilities to store information in magnetic structures. Understanding their nucleation and propagation is also of interest in basic research. While vortices are usually examined in particles of homogeneous material, here we give an overview of the impact of borders between two materials, i.e. iron and permalloy, on magnetization reversal and vortex formation in double-wedges as well as adjacent rectangles of different thickness. While former investigations of pure iron nanoparticles of similar dimensions revealed different magnetization reversal magnetisms without vortex, with one or two vortices, the addition of a permalloy part stabilized the magnetization reversal so that in all situations under investigation, a single vortex was observed. Our simulations underline the technological importance of such double-material structures for the preparation of nanostructures for storage devices with reliable magnetization reversal processes, stable against erroneous modifications of nanoparticle dimensions and magnetic field orientations. [ABSTRACT FROM AUTHOR]

• Redox reaction between Co and CoO x. • Another voltage controlled magnetic storage scheme with data encoded in nanoparticle size. • Superparamagnetism can be used in magnetic storage. Electrochemical reaction induced by gate voltage between metallic cobalt and cobalt oxides was found to remarkably reshape average volume of superparamagnetic particles in Pt/Co/AlO x stacks at room temperature and thus modulate superparamagnetic properties, such as saturation fields and saturated magnetization, of the superparamagnetic films. The interfacial reaction was indicated in anomalous Hall transport measurement. This voltage-controllable superparamagnetism observed in Pt/Co/AlO x films could be utilized in a new architecture of nonvolatile and high density magnetic random access memories or neuromorphic computing. [ABSTRACT FROM AUTHOR]

• The magnetic anisotropy energies of doped monolayer MoS 2 are obtained. • The physical origins of magnetic anisotropy are revealed. • The distributions of magnetic anisotropy energy are clearly shown in k-space. • The Co-doped MoS 2 monolayer has potential for magnetic storage applications. Magnetic anisotropies of Mn-, Fe- and Co-doped monolayer MoS 2 at Mo-site have been investigated by first-principles calculations. The results demonstrate that the preferential axis of magnetization is perpendicular to the MoS 2 monolayer for Fe dopant, while in-plane for Mn and Co dopants. Especially, the magnetic anisotropy energy (MAE) of the Co-doped system can reach −3.58 meV, whose absolute value is the largest among these systems. The analyses of microscopic origin of MAE are based on the second-order interactions of spin-orbit coupling (SOC) between the occupied and unoccupied states near the Fermi level. Additionally, the MAE distributions of doped systems are clearly shown in the reciprocal space. Finally, the fitted curves of the angular dependence of total energy for these systems strongly support our argument. Our research may assist in designing new spintronic devices. [ABSTRACT FROM AUTHOR]

• Repeatable 180° magnetization switchings can directly induced by voltage pulse without a bias magnetic field. • The initial switching time is short, which is about 1/5 of the existing research scheme. • Optimal voltage pulse waveform and tilt angle is obtained by micromagnetic method. • Repeated switching at room temperature is calculated by mathematical model. Fast 180° magnetization switching is one of the main challenges for straintronics to be used in magnetic storage and logic. By deflecting the electrodes pair axis by a small angle from the long axis of a uniaxial multiferroic nanomagnet, the voltage pulse can directly induce the nanomagnet to complete repeatable 180° switchings without requiring a start-up time. The dynamic magnetization of the repeatable 180° switching in the nanomagnet and the optimal voltage pulse waveform is simulated through micromagnetic method. Is obtained by simulation calculation, when the electrodes pair axis tilting angle is about 5°, the required stress is small, the switching frequency is high, and the initial switching time is short, which is about 1/5 of the existing research scheme. The switching at room temperature is also calculated by a mathematical model. The switching time is longer under the influence of thermal fluctuations. These findings may provide guidance for the application of straintronic devices. [ABSTRACT FROM AUTHOR]

• Nano-sized magnetite (Fe 3 O 4) particles are synthesized using co-precipitation method. • MR gels are prepared using synthesized magnetite particles for various mass fractions. • The characterization of the MR gels have been performed for prepared MR gels. • The influence of the size on the magnetite based MR gels are studied and are compared with carbonyl iron (CI) based MR gels. • As the size of the particles increases, an increasing trend in saturation magnetization values is observed. Magnetorheological (MR) gels are a class of smart materials whose mechanical characteristics can be modified by the application of an external magnetic field. This paper aims at the investigation of the effect of the size of spherically shaped particles on the magnetorheological gels and the significance of its influence on the properties of the MR gels. MR gels are prepared using magnetite (Fe 3 O 4) nanoparticles and/or carbonyl iron (CI) microparticles dispersed in a polymer gel. A free decay test apparatus built in-house is used to obtain the magnetic field dependent shear response of the gels under dynamic conditions at room temperature and the results are compared for varying sizes of particles. The results indicate a clear trend of increase in storage modulus of the magnetic gel with the decrease in the size of the particles under same conditions of magnetic field and mass fraction. For example, the increase in the shear storage moduli of the magnetic gel, prepared with a mass fraction of 20% of carbonyl iron particles of sizes 3.4 μm and 1.4 μm increase by 16.3% and 18% respectively of the zero field moduli, while the gel with the same mass fraction of magnetite nanoparticles increases to 28%. [ABSTRACT FROM AUTHOR]

Abstract: We have succeeded in aligning self-assembled structures by using a lithographically defined stripe. The 140nm wide by 100nm high SiO2 strip is shown to guide the assembly of 500nm latex spheres so that spheres are aligned along the strip and are in registration on either side of the strip. This method can be used to increase long-range ordering in magnetic storage systems without compromising the density. Inverse sphere Ni arrays were made by electrodeposition through the latex template. We also show that the hexagonal symmetry of the resulting inverse sphere Ni arrays can be simulated using the approach presented below. [Copyright &y& Elsevier]