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This study examines the application of machine learning algorithms, specifically the Random Forest regression model, to optimize the magnetocaloric effect in all- d -metal Heusler alloys. The model was trained using descriptors related to the mean properties of individual atoms, the properties of simple compounds in their ground state, and measures of chemical disorder. It demonstrated high accuracy in predicting structural properties, while exhibiting moderate accuracy in predicting magnetic properties. To identify optimal alloy compositions, a genetic algorithm was used to find those with the greatest differences in magnetization during martensitic transitions. Using this combined approach, the Ni–Co–Mn–Ti alloy system was thoroughly explored, resulting in the discovery of an alloy with a maximum magnetization difference. These results are consistent with previous research based on density functional theory and highlight the effectiveness of integrating machine learning with genetic algorithms for the discovery of new materials with outstanding magnetocaloric properties. The study emphasizes the need for further refinement of models capable of accurately predicting complex magnetic interactions, which is essential for fully leveraging the potential of all- d -metal Heusler alloys in practical applications. [ABSTRACT FROM AUTHOR]

The van der Waals itinerant ferromagnet Fe5GeTe2 has recently aroused great attention for the promising in spintronic devices applications. For such applications, the intrinsic magnetic properties such as magnetocrystalline anisotropy and room-temperature Curie temperature play the key role, both of which depend on the localized feature of its itinerant 3d electrons of Fe. Here, we study the localized feature of the itinerant 3d electrons of Fe of Fe5GeTe2. The results of Fe5GeTe2 single crystal show that the inverse susceptibility well fits the Curie–Weiss law above the paramagnetic Curie temperature TΔ ≈ 300 K, and the saturated magnetization follows a spin wave model with a power law of 1.525 below 30 K, both of which identify the strongly localized feature. Furthermore, the Rhodes–Wohlfarth ratio of approximately 2.4 of Fe5GeTe2 is higher than the value of 2.14 of vdW itinerant ferromagnet Fe3GeTe2, implying that the localized extent of the former is slightly lower than the latter. [ABSTRACT FROM AUTHOR]

The study of magnetic interactions is crucial in understanding magnetic materials, where both exchange coupling and dipole interactions significantly affect the magnetic properties of composite materials. Separating and utilizing these two types of interactions have consistently been a research focus. In this study, FINEMET/Fe35Ni65 composite ribbons with varying coating thicknesses were fabricated using magnetron sputtering. Notably, obvious four-peak giant magnetoimpedance profiles can be observed as the Fe35Ni65 film thickness varied from 10 to 50 nm. Additionally, the manifestation of the four-peak profile was attributed to the variation in the magnetic properties in the FINEMET ribbon induced by exchange coupling and dipole interaction. This analysis is crucial for advancing our understanding of the underlying physical mechanisms of magnetic interactions in composite ribbons. [ABSTRACT FROM AUTHOR]

The van der Waals itinerant ferromagnet Fe5GeTe2 has recently aroused great attention for the promising in spintronic devices applications. For such applications, the intrinsic magnetic properties such as magnetocrystalline anisotropy and room-temperature Curie temperature play the key role, both of which depend on the localized feature of its itinerant 3d electrons of Fe. Here, we study the localized feature of the itinerant 3d electrons of Fe of Fe5GeTe2. The results of Fe5GeTe2 single crystal show that the inverse susceptibility well fits the Curie–Weiss law above the paramagnetic Curie temperature TΔ ≈ 300 K, and the saturated magnetization follows a spin wave model with a power law of 1.525 below 30 K, both of which identify the strongly localized feature. Furthermore, the Rhodes–Wohlfarth ratio of approximately 2.4 of Fe5GeTe2 is higher than the value of 2.14 of vdW itinerant ferromagnet Fe3GeTe2, implying that the localized extent of the former is slightly lower than the latter. [ABSTRACT FROM AUTHOR]

The spontaneous exchange bias effect (SEB) has wide application prospects in information storage technologies. In this study, nanoscale raw materials were used to fabricate antiferromagnetic Fe3BO6 polycrystals. The obtained Fe3BO6 exhibited a large SEB effect, where the value of the spontaneous exchange bias field at room temperature was as large as ∼4234 Oe. The room-temperature training effect, temperature-dependence, and maximum field-dependence of the HSEB were investigated. We propose that this giant SEB originates from the exchange-coupling interactions between the weak ferromagnetic surface state and the bulk antiferromagnetic state. The theoretical analysis results were further verified by comparing the magnetic properties of the Fe3BO6 with relatively low crystallinity. The results of this investigation will help find promising candidate materials for devices based on the SEB effect. [ABSTRACT FROM AUTHOR]

The present study probes the effect of cation distributions in the structural, optical, electronic, and magnetic properties of mixed-valent inverse-spinel NiCo2O4 (NCO) nanoparticles (NPs). NCO NPs were prepared using the sol–gel combustion method and the grain size was obtained in the magnetic exchange length range assumed to be from single-ion anisotropy. The Raman and photoluminescence spectroscopies confirm the presence of an inverse-spinel structure with different oxidation states, and vibrating sample magnetometry clarifies the existence of ferromagnetism with the presence of magnetic anisotropy among the cations. These NPs annealed at a higher grain-growth temperature accumulate ferrimagnetic properties and produce magneto-crystalline anisotropy making NCO an assuring material for spintronic applications. A detailed x-ray absorption spectroscopy and x-ray magnetic circular dichroism studies reveal an indestructible correlation between the distribution of the present cations and the element-specific origin of ferrimagnetic behavior. Ni is found to be accountable for the magnetic moment and electronic conduction, whereas Co is associated mainly with the generation of the magnetic anisotropy even in the polycrystalline NP form. This describes the anti-ferromagnetic coupling between Co and Ni ions that is pivotal in demonstrating the exchange interaction between these cations. The above result signifies the site-dependent cation valence states for the magnetic properties, and the extent of growing conditions are related to such cation-site dysfunction. This depicts further tunability in NCO as a functional oxide material. [ABSTRACT FROM AUTHOR]

The influence of shape, orientation, and motion patterns of magnetic domains in nanocrystalline strips with a high Ni content on soft magnetic properties was studied using normal isothermal annealing and transverse magnetic field annealing (TFA). The results indicate that TFA-10 (with 10 at. % Ni) exhibits the lowest coercivity (Hc) at 0.33 A/m and a remanence ratio (Br/Bm) of 0.2%. Moreover, more stringent conditions for the anisotropy field (Hk) are applied, and the resistance to current bias is assessed by examining the relationship between the field-induced magnetic anisotropy (Ku) and the current magnitude. A highly linear hysteresis loop with an anisotropy field (Hk) of 210 A/m was achieved, resulting in an effective permeability (μe) of 5000 at 500 kHz and 0.5 V. Furthermore, the current required to maintain a 100% bias ratio is determined to be up to 12 A. This study demonstrates the excellent soft magnetic properties of TFA-10 and guides optimizing the constant permeability properties of nanocrystalline alloys. [ABSTRACT FROM AUTHOR]

The impact of high-temperature annealing on the magnetic and microstructural properties of MnFePSi glass-coated microwires is studied. A comparative analysis is conducted to elucidate the influence of annealing conditions (temperature and time) on physical characteristics MnFePSi glass-coated microwires compared to the as-prepared sample. The results reveal a significant influence of the annealing process on MnFePSi-based glass-coated microwires. A notable observation is the increased coercivity (Hc) for the sample annealed at 973 K for 1 h, rising from 761 Oe (as-prepared) to 1200 Oe. However, increasing the annealing time to 2 h leads to a sharp reduction in the coercivity value to 253 Oe. Thermomagnetic curves [field-cooling (FC) and field-heating (FH)] of the annealed samples, measured at both low and high magnetic fields, exhibit perfect matching. This indicates that the relevant contribution of the internal stresses induced by glass coating in the magnetic behavior in both FC and FH protocols. We demonstrate the possibility for tailoring and modification of relevant magnetic phenomena such as metamagnetic phase transition, magnetic behavior, and the control of magnetic response (hardness/softness). These tailored properties pave the way for the exploitation of MnFePSi glass-coated microwire in a wide range of glass-coated microwire applications. [ABSTRACT FROM AUTHOR]

This study investigates the effects of Zn substitution on the magnetic properties of ∼5 nm cobalt ferrite nanoparticles (ZnxCo1−xFe2O4, where x = 0, 0.13, 0.34, and 0.55), demonstrating that Zn substitution induces complex changes in spin canting and prompts a redistribution of cations among the sublattices. We reconstructed the magnetic structure of these spinel ferrites by integrating the classical two-sublattice Néel model of ferrimagnetism with the data obtained from 57Fe Mössbauer spectrometry. Consequently, this research provides a comprehensive understanding of how Zn substitution tunes the magnetic properties of CoFe2O4 nanoparticles, offering valuable insights into the development of magnetic materials with tailored properties for various applications. [ABSTRACT FROM AUTHOR]

The inherent flexibility of two-dimensional (2D) materials allows for efficient manipulation of their physical properties through strain application, which is essential for the development of advanced nanoscale devices. This study aimed to understand the impact of mechanical strain on the magnetic properties of two-dimensional (2D) materials using Monte Carlo simulations. The effects of several strain states on the magnetic properties were investigated using the Lennard-Jones potential and bond length-dependent exchange interactions. The key parameters analyzed include the Lindemann coefficient, radial distribution function, and magnetization in relation to temperature and magnetic field. The results indicate that applying biaxial tensile strain generally reduces the critical temperature (Tc). In contrast, the biaxial compressive strain increased Tc within the elastic range, but decreased at higher strain levels. Both compressive and tensile strains significantly influence the ferromagnetic properties and structural ordering, as evidenced by magnetization hysteresis. Notably, pure shear strain did not induce disorder, leaving the magnetization unaffected. In addition, our findings suggest the potential of domain-formation mechanisms. This study provides comprehensive insights into the influence of mechanical strain on the magnetic behavior and structural integrity of 2D materials, offering valuable guidance for future research and advanced material design applications. [ABSTRACT FROM AUTHOR]

Epitaxial films of BiAl x Fe 1 − x O 3 (xBAFO) were grown on SrTiO 3 (STO) and SrRuO 3 buffered STO substrates using pulsed laser deposition. To understand the effects of Al substitution at the Fe-site of BFO, we systematically investigated its impact on the material's crystal structure, surface morphology, ferroelectric properties, and magnetic properties. Our x-ray diffraction analysis revealed that phase-pure xBAFO films can be stabilized for Al concentrations between 0% and 35%, without the formation of secondary phases, due to the isotypic crystal structures of BiAlO 3 and BiFeO 3. This allowed the rhombohedral structure of BAFO to be preserved. We then characterized the ferroelectric properties of xBAFO (0 ≤ x ≤ 0.25) by analyzing polarization-voltage hysteresis loops, which exhibited a transition from a nearly square shape to a more slanted shape with increasing Al substitution. Additionally, piezoresponse force microscopy revealed that the domain growth mode, shape, size, dimension, and nucleation play a crucial role in the switching behavior of ferroelectric materials. Furthermore, we observed a modest enhancement in magnetization due to the modified spin ordering of Fe atoms with Al substitution. Notably, the optimal ferroelectric and magnetic properties were achieved at an Al concentration of 15%. These findings suggest that BAFO is a promising magnetoelectric material with desired functionalities for realizing BFO-based next-generation non-volatile memory devices. [ABSTRACT FROM AUTHOR]

In this study, the excellent Y2−xNdxFe17 (x = 0, 0.2, 0.4, 0.6, 0.8) magnetic particles were prepared by the reduction–diffusion process. Through the ferromagnetic coupling between light rare earth element Nd and Fe atoms, we effectively modulated the magnetic crystallographic anisotropy of Y2Fe17. As the amount of Nd doping increases, the natural resonance frequency of Y2−xNdxFe17/PU increases to 15.7 GHz, the saturation magnetization increases to 120.43 emu/g, the Curie temperature increases to 390 K, and the average hyperfine field also increases to 22.5 T. Notably, the doping of Nd atoms leads to a slight expansion of the Y2−xNdxFe17 lattice, exhibiting distinct anisotropic characteristics that preferentially develop along the basal plane. The doping of rare earth Nd atoms with strong magnetic crystal anisotropy can not only significantly enhance the easy-plane magnetic crystallographic anisotropy, causing the natural resonance peak to shift toward higher frequencies, but also has important guiding significance for broadening the high-frequency application range of easy-plane rare earth transition metal alloys. This achievement provides new ideas and methods for the design and development of high-performance magnetic materials. [ABSTRACT FROM AUTHOR]

In this study, the excellent Y2−xNdxFe17 (x = 0, 0.2, 0.4, 0.6, 0.8) magnetic particles were prepared by the reduction–diffusion process. Through the ferromagnetic coupling between light rare earth element Nd and Fe atoms, we effectively modulated the magnetic crystallographic anisotropy of Y2Fe17. As the amount of Nd doping increases, the natural resonance frequency of Y2−xNdxFe17/PU increases to 15.7 GHz, the saturation magnetization increases to 120.43 emu/g, the Curie temperature increases to 390 K, and the average hyperfine field also increases to 22.5 T. Notably, the doping of Nd atoms leads to a slight expansion of the Y2−xNdxFe17 lattice, exhibiting distinct anisotropic characteristics that preferentially develop along the basal plane. The doping of rare earth Nd atoms with strong magnetic crystal anisotropy can not only significantly enhance the easy-plane magnetic crystallographic anisotropy, causing the natural resonance peak to shift toward higher frequencies, but also has important guiding significance for broadening the high-frequency application range of easy-plane rare earth transition metal alloys. This achievement provides new ideas and methods for the design and development of high-performance magnetic materials. [ABSTRACT FROM AUTHOR]

Magnetic characteristics, magnetocaloric effect, and critical behavior of Nd1−xSrxMnO3 compounds by Sr doping (x = 0.2, 0.3, 0.4, 0.5) were studied. All samples maintained orthorhombic structures, but the space group changed from Pnma (No. 62) for x = 0.2, 0.3 to Imma (No. 74) for x = 0.4, 0.5. As Sr doping increased, the Curie temperature (TC), Curie–Weiss temperature (TCW), and magnetization increased, attributed to the double exchange (DE) interaction. A discrepancy between TCW and TC was observed due to the competition between polarons and DE interaction. The critical behavior was investigated systematically using the self-consistent (modified Arrott plots, MAP) method and the Kouvel–Fisher (KF) relation. The KF relation was suitable for the samples with x = 0.2 and 0.5, while the MAP method was suitable for the samples with x = 0.3 and 0.4. Among the Ising, XY, Heisenberg, and mean-field models, the samples with x = 0.2, 0.3, and 0.4 aligned more closely with the mean-field model, except for the x = 0.5 sample. Entropy change (−ΔSM) of Nd1−xSrxMnO3 (0.2 ≤ x ≤ 0.5) increased with the applied field, with the maximum value observed around TC. For the sample with x = 0.3, (−ΔSM) reached 4.315 J/kg K at μ0ΔH = 50 kOe, corresponding to a relative cooling power (RCP) of 280.48 J/kg. Remarkably, the x = 0.4 sample displayed (−ΔSM) of 3.298 J/kg K at μ0ΔH = 50 kOe near room temperature, with the RCP of 283.64 J/kg. These findings underscore the role of Sr doping in tuning the magnetic properties, critical behavior, and magnetocaloric effect of NdMnO3. [ABSTRACT FROM AUTHOR]

Nanostructures possessing plasmonic and magnetic properties can enhance the transverse magneto-optical Kerr effect (TMOKE) by exciting surface plasmon resonances (SPRs). This provides a promising platform for magneto-optical SPR sensors with significantly improved sensing performance. Here, we propose a high-performance magneto-optical SPR sensor, which consists of a bilayer Au/Co grating placed on a gold film. By tuning the structural parameters, a Fano-like TMOKE spectrum with a linewidth of only 0.0135 nm and an amplitude approaching the theoretical maximum is obtained. We attribute the optimal TMOKE signal achieved by the sensor to the critical coupling concept which is associated with the trade-off between scattering and intrinsic decay rates of the system. The optimized nanostructure sensor demonstrates a sensitivity of 1432 nm/RIU to refractive index fluctuations as small as 0.0001 in air, and all figures of merit (FOM) up to 105 RIU−1, making it suitable for gas sensor fabrication. [ABSTRACT FROM AUTHOR]

Magnetic gels with embedded micro-/nano-sized magnetic particles in cross-linked polymer networks can be actuated by external magnetic fields, with changes in their internal microscopic structures and macroscopic mechanical properties. We investigate the responses of such magnetic gels to an external magnetic field, by means of coarse-grained molecular dynamics simulations. We find that the dynamics of magnetic particles are determined by the interplay of magnetic dipole–dipole interactions, polymer elasticity, and thermal fluctuations. The corresponding microscopic structures formed by the magnetic particles, such as elongated chains, can be controlled by the external magnetic field. Furthermore, the magnetic gels can exhibit reinforced macroscopic mechanical properties, where the elastic modulus increases algebraically with the magnetic moments of the particles in the form of ∝ (m − m c ) 2 when magnetic chains are formed. This simulation work can not only serve as a tool for studying the microscopic and the macroscopic responses of the magnetic gels, but also facilitate future fabrications and practical controls of magnetic composites with desired physical properties. [ABSTRACT FROM AUTHOR]

The effects of sintering temperature (Ts) and chemical substitution on the structural and magnetic properties of manganite compounds L a 1 − x S r x M n 1 − y F e y O 3 (0.025 ≤ x ≤ 0.7 ; y = 0.01 , 0.15) are explored in a search to optimize their magnetocaloric properties around room temperature. A ferromagnetic (FM) to paramagnetic (PM) phase transition is observed at a Curie temperature Tc that can be controlled to approach room temperature by Sr and Fe substitution, but also by adjusting the sintering temperature Ts. Accordingly, the magnetic entropy change (− Δ S M ) quantifying the magnetocaloric effect (MCE) presents a peak at or close to Tc that shifts and broadens with both Sr and Fe doping and is further tuned with sintering temperature. Altogether, we show that it is possible to adjust the strength and dominance of the ferromagnetic coupling in these ceramics, but also using disorder as a tool to broaden and adjust the temperature range with a significant magnetic entropy change. [ABSTRACT FROM AUTHOR]

Room temperature ferromagnetism observed in polycrystalline MnGeP2 bulk samples was investigated by different experimental techniques. The magnetization measurements show a high temperature ferromagnetic phase with a critical temperature TC = 294.0 K and a low temperature magnetic phase transition at TN = 40.5 K. As these parameters (TC,TN) correspond to those of MnP, a ferromagnetic half-metal, whose composition of the samples was further characterized by x-ray diffraction and Rutherford backscattering measurements. They confirmed the presence of orthorhombic MnP precipitates. Electron paramagnetic resonance (EPR) and ferromagnetic resonance (FMR) measurements in the temperature range of T = 4 K to T = 380 K confirm the attribution of the magnetic phase to MnP and show no additional EPR or FMR signal associated with MnGeP2. We conclude that the magnetic properties of the polycrystalline MnGeP2 bulk samples grown by the horizontal gradient freeze technique are dominated by MnP inclusions and that phase pure chalcopyrite MnGeP2 is not ferromagnetic in contrary to previous reports. [ABSTRACT FROM AUTHOR]

Quasi-one-dimensional topological materials have emerged as a captivating area of research due to their interesting electronic properties and potential applications. NbNiTe 5 is one such quasi-1D material. In this work, we report the synthesis, structural characterization, and comprehensive investigation of the electrical transport and magnetic properties of NbNiTe 5. NbNiTe 5 crystallizes in the orthorhombic crystal system with the C m c m space group. Experimental studies have uncovered metallic nature with a remarkably high residual resistivity ratio of 103, along with intriguing spin–orbit interaction-driven nonsaturating magnetotransport properties at low temperatures. A meticulous analysis incorporating magnetoconductivity measurements unveils signatures of weak anti-localization analyzed by using the Hikami–Larkin–Nagaoka formula. Furthermore, the de Haas–van Alphen oscillations demonstrate the high mobility of charge carriers with a significantly low effective mass at five frequencies: F α = 84.82 T, F β = 131.21 T, F γ = 242.36 T, F δ = 31.93 T, and F δ ′ = 162.33 T. In light of these collective findings, NbNiTe 5 can be defined as a quasi-1D topological semimetal. [ABSTRACT FROM AUTHOR]

The effects of sintering temperature (Ts) and chemical substitution on the structural and magnetic properties of manganite compounds L a 1 − x S r x M n 1 − y F e y O 3 (0.025 ≤ x ≤ 0.7 ; y = 0.01 , 0.15) are explored in a search to optimize their magnetocaloric properties around room temperature. A ferromagnetic (FM) to paramagnetic (PM) phase transition is observed at a Curie temperature Tc that can be controlled to approach room temperature by Sr and Fe substitution, but also by adjusting the sintering temperature Ts. Accordingly, the magnetic entropy change (− Δ S M ) quantifying the magnetocaloric effect (MCE) presents a peak at or close to Tc that shifts and broadens with both Sr and Fe doping and is further tuned with sintering temperature. Altogether, we show that it is possible to adjust the strength and dominance of the ferromagnetic coupling in these ceramics, but also using disorder as a tool to broaden and adjust the temperature range with a significant magnetic entropy change. [ABSTRACT FROM AUTHOR]

Room temperature ferromagnetism observed in polycrystalline MnGeP2 bulk samples was investigated by different experimental techniques. The magnetization measurements show a high temperature ferromagnetic phase with a critical temperature TC = 294.0 K and a low temperature magnetic phase transition at TN = 40.5 K. As these parameters (TC,TN) correspond to those of MnP, a ferromagnetic half-metal, whose composition of the samples was further characterized by x-ray diffraction and Rutherford backscattering measurements. They confirmed the presence of orthorhombic MnP precipitates. Electron paramagnetic resonance (EPR) and ferromagnetic resonance (FMR) measurements in the temperature range of T = 4 K to T = 380 K confirm the attribution of the magnetic phase to MnP and show no additional EPR or FMR signal associated with MnGeP2. We conclude that the magnetic properties of the polycrystalline MnGeP2 bulk samples grown by the horizontal gradient freeze technique are dominated by MnP inclusions and that phase pure chalcopyrite MnGeP2 is not ferromagnetic in contrary to previous reports. [ABSTRACT FROM AUTHOR]

The Mn3AgN-based manganese nitrides have attracted continuous attention due to the interesting functional properties, which is closely correlated with the magnetic evolution coupling with structural and electrical order. However, the attention on the fundamental magnetic behavior of the Mn3AgN matrix is still insufficient up to now. Here, the magnetic properties of Mn3AgN have been investigated by comprehensive magnetic measurements including dc magnetization, ac susceptibility, and magnetic relaxation. The results show that Mn3AgN undergoes two magnetic transitions with decreasing temperature: the transition from paramagnetic to antiferromagnetic (AFM) state at ∼285 K and from AFM to spin-glass-like (SGL) state at ∼110 K. The SGL state is essentially a mixed magnetic state of weak short-range ferromagnetic order and spin glass, and its appearance should be related to the AFM configuration of Γ4g with ferromagnetic component. The unique low-temperature magnetic structure of Mn3AgN makes it exhibit interesting low temperatures magnetic behavior, such as the magnetic irreversibility phenomenon, magnetic relaxation behavior, and so on. [ABSTRACT FROM AUTHOR]

High-performance and stable spintronic devices have garnered considerable attention in recent years. Based on first-principle and Monte Carlo calculations, we demonstrate that under reasonable carrier doping, H-VSe2 exhibits 100% spin polarization, a magnetic anisotropy energy of 581 μeV, a tunable easy-axis, and a Curie temperature of 330 K. Moreover, Dzyaloshinskii–Moriya interactions in H-VSe2 and magnetic hysteresis loops are determined theoretically for the first time, which provides more precise and comprehensive descriptions of its magnetic properties under finite temperatures and external magnetic field. This work suggests that H-VSe2 is a powerful candidate for spintronic devices, and it provides solid theoretical support for future experiments. [ABSTRACT FROM AUTHOR]

Magnons are quasiparticles of spin waves, carrying both thermal energy and spin information. Controlling magnon transport processes is critical for developing innovative magnonic devices used in data processing and thermal management applications in microelectronics. The spin ladder compound S r 14 C u 24 O 41 with large magnon thermal conductivity offers a valuable platform for investigating magnon transport. However, there are limited studies on enhancing its magnon thermal conductivity. Herein, we report the modification of magnon thermal transport through partial substitution of strontium with yttrium (Y) in both polycrystalline and single crystalline S r 14 − x Y x C u 24 O 41. At room temperature, the lightly Y-doped polycrystalline sample exhibits 430% enhancement in thermal conductivity compared to the undoped sample. This large enhancement can be attributed to reduced magnon-hole scattering, as confirmed by the Seebeck coefficient measurement. Further increasing the doping level results in negligible change and eventually suppression of magnon thermal transport due to increased magnon-defect and magnon-hole scattering. By minimizing defect and boundary scattering, the single crystal sample with x = 2 demonstrates a further enhanced room-temperature magnon thermal conductivity of 19 W m − 1 K − 1 , which is more than ten times larger than that of the undoped polycrystalline material. This study reveals the interplay between magnon-hole scattering and magnon-defect scattering in modifying magnon thermal transport, providing valuable insights into the control of magnon transport properties in magnetic materials. [ABSTRACT FROM AUTHOR]

The easy-plane FeSi3.5 composite with excellent magnetic properties and power loss is proposed. The magnetic properties and power loss of the easy-plane FeSi3.5 composite are studied by using the none easy-plane FeSi3.5 composite as a control. This easy-plane FeSi3.5 composite has an initial permeability of 62, resonance frequencies of 100 MHz and 1.5 GHz, and frequency stability of 40 MHz. In addition, the easy-plane FeSi3.5 composite has also excellent loss properties, with a high-frequency power loss of only 108.12 kW/m3. The three kinds of power loss of the easy-plane FeSi3.5 composite are reduced compared with the none easy-plane FeSi3.5 composite through loss separation, especially the eddy current loss and the excess loss. The eddy current loss and the excess loss of the easy-plane FeSi3.5 composite are only 0.03 and 12.93 kW/m3 at 500 kHz, which reduce by 99.44% and 92% compared with the none easy-plane FeSi3.5 composite. Effective reduction of power loss and significant improvement of magnetic properties are important for solving the problem of power loss encountered by power electronic devices at the kHz band. Therefore, the application of the easy-plane FeSi3.5 composite with excellent power loss and high-frequency magnetic properties becomes a novel approach to meet the practical application of power electronics. The method that increases the working frequency and decreases the maximum magnetic flux density keeping the energy transformation efficiency constant is a new method to reduce power loss at the wide frequency band. [ABSTRACT FROM AUTHOR]

The mixed zinc-ferrite spinel magnetic nanoparticles (MNPs) with the general formula ZnxFe3−xO4 are among the most extensively studied families of Fe oxides due to their interesting and diverse chemical, electronic, and magnetic properties. These systems offer the possibility of surface functionalization and possess high biocompatibility, making them highly attractive for applications in biomedicine, such as magnetic fluid hyperthermia (MFH). The efficiency of the MFH process relies on the magnetic, structural and morphological properties of the MNPs. The substitution with the Zn ion and the cationic distribution, as well as the synthesis process employed, have a direct impact on the final properties of these oxides. Therefore, it is essential to have tools that enable a comprehensive characterization of the system to assess its performance in MFH. In this study, we have synthesized four ZnxFe3−xO4 MNP systems using three different methods: two by thermal decomposition at high temperatures, one by co-precipitation, and another by co-precipitation followed by ball milling. We analyze the effect of these various synthesis processes on the magnetic and crystallographic properties, aiming to correlate them with the response of each system in MFH. Neutron diffraction data are employed to determine the cation site occupation and to investigate the correlation with the synthesis method. MFH measurements were conducted in media of diverse viscosities, revealing different values of specific loss power, thus demonstrating a clear dependence on the synthesis process and Zn content. [ABSTRACT FROM AUTHOR]

The study of anisotropic magnetoresistance (AMR) holds dual significance in both theoretical and applied contexts. The underlying mechanisms of AMR remain unclear, and the phenomenon of AMR sign reversal (positive and negative transitions in values) has garnered multiple interpretations, demanding experimental verification. In this work, the effect of epitaxial strain on magnetic and transport properties of perovskite manganese oxide La0.35Sr0.65MnO3 films is investigated. The AMR demonstrates sign reversal and symmetry change behaviors. The symmetry changes of AMR stem from the competition between Zeeman energy, exchange interaction energy, and magnetocrystalline anisotropy energy. The sign reversal of AMR is attributed to the change in the density of states of spin up and spin down of conduction electrons during the magnetic phase transition induced by epitaxial strain. Our work offers experimental evidence and a reasonable explanation for the origin of the sign reversal of AMR. [ABSTRACT FROM AUTHOR]

Magnons are quasiparticles of spin waves, carrying both thermal energy and spin information. Controlling magnon transport processes is critical for developing innovative magnonic devices used in data processing and thermal management applications in microelectronics. The spin ladder compound S r 14 C u 24 O 41 with large magnon thermal conductivity offers a valuable platform for investigating magnon transport. However, there are limited studies on enhancing its magnon thermal conductivity. Herein, we report the modification of magnon thermal transport through partial substitution of strontium with yttrium (Y) in both polycrystalline and single crystalline S r 14 − x Y x C u 24 O 41. At room temperature, the lightly Y-doped polycrystalline sample exhibits 430% enhancement in thermal conductivity compared to the undoped sample. This large enhancement can be attributed to reduced magnon-hole scattering, as confirmed by the Seebeck coefficient measurement. Further increasing the doping level results in negligible change and eventually suppression of magnon thermal transport due to increased magnon-defect and magnon-hole scattering. By minimizing defect and boundary scattering, the single crystal sample with x = 2 demonstrates a further enhanced room-temperature magnon thermal conductivity of 19 W m − 1 K − 1 , which is more than ten times larger than that of the undoped polycrystalline material. This study reveals the interplay between magnon-hole scattering and magnon-defect scattering in modifying magnon thermal transport, providing valuable insights into the control of magnon transport properties in magnetic materials. [ABSTRACT FROM AUTHOR]

We examine structural and magnetic properties of a series of La–Fe–Si alloys in the region of concentrations where they naturally form two-phase LaFeSi–LaFe13−xSix composites with variable content and connectivity of LaFe13−xSix grains distributed within the LaFeSi matrix. Theoretical calculations confirm that the LaFeSi constituent is magnetically and structurally inert below room temperature and at pressures between −10 and 10 GPa. The LaFe13−xSix constituent, on the other hand, is magnetically and structurally active: it exhibits first-order magnetostructural transformations that, in addition to xSi, can be controlled with temperature, magnetic field, and pressure. In composites where the concentration of the inactive constituent is ∼70 wt. % or greater, the standard, single-step, LaFe13−xSix first-order phase transformation proceeds in two steps separated by over 30 K in a zero magnetic field. Increasing the magnetic field recouples the two steps and restores the single-step phase transformation pathway. We analyze the roles of stresses caused by both thermal expansion mismatch and the first-order magnetic phase transition in LaFe13−xSix to rationalize the observed physical behaviors that emerge as the temperature or/and magnetic field vary. [ABSTRACT FROM AUTHOR]

Neodymium (Nd) magnets (Nd 2 Fe 14 B) are key materials for achieving high energy conversion efficiency. The coercive forces (fields) of the magnets are often reinforced by adding dysprosium (Dy), especially at high temperatures. To understand the magnetic properties of Dy-substituted systems (Nd 1 − x Dy x) 2 Fe 14 B, it is important to study those of Dy 2 Fe 14 B and Nd 2 Fe 14 B and analyze the difference in detail from a microscopic viewpoint. Applying a recently developed atomistic model approach, we investigated thermodynamic properties of these magnets. We studied the temperature and field dependences of the magnetizations, and anisotropy fields and energies. We found that the simulation results captured the characteristic features of the experimentally observed data. We discuss the detail with the magnetization profiles of the component atoms. Furthermore, we investigated the effect of Dy random substitution on the coercivity in two systems: one in contact with vacuum and the other in contact with a grain boundary phase. We found that the threshold fields increased almost linearly with the concentration of Dy atoms in both systems, which was compared to the results of the layer-by-layer substitution effect analyzed in our previous work. We discuss the influence of the arrangement of Dy atoms on coercivity enhancement. [ABSTRACT FROM AUTHOR]

We investigated the magnetic properties of Sendust (Fe-Al-Si) alloys not only at 0 K but also at finite temperatures by means of the first-principles calculations assuming A2, B2, and D 0 3 structures. We confirmed that the itinerant characteristics of 3 d electrons of Fe are not negligible and a significantly small exchange stiffness constant exists at zero temperature in a B2 structure. However, the calculated Curie temperatures are in the same order for all structures; this indicates that the Curie temperature cannot be determined only by the exchange interactions at zero temperature in itinerant electron systems. Temperature dependence of the exchange interaction, namely, spin configuration dependence, also might be important for determining it. In addition, this property might also be related to the unique behavior of the temperature dependence of the exchange stiffness constant for the B2 structure, which does not decrease monotonically as temperatures increase, contrary to the behavior expected from the Heisenberg model. In addition, we investigated composition dependence on the exchange stiffness constant at zero temperature and confirmed that the substitution of Si with Al could improve the amplitude of the exchange stiffness constant at zero temperature for all structures. [ABSTRACT FROM AUTHOR]

We introduce a novel water bath hydrogenation process designed to enhance the magnetic properties and hyperfine field of Y2Fe17. The core of this process lies in the successful preparation of a new compound Y2Fe17H3.5 by introducing hydrogen in a mild water bath environment, accomplished by a chemical reaction between calcium, Y2Fe17, and ammonium acetate solution at room temperature and pressure. After hydrogen doping, cell volume expansion increased from 778.511 to 795.383 Å3, and notably, lattice expansion is anisotropic. Furthermore, saturation magnetization is increased from 103 to 134.93 emu/g, Curie temperature is increased from 320 to 461 K, and the average hyperfine field is increased from 18 to 25 T. The improvement in magnetic properties is due to the increase in Fe–Fe distance, which according to the Bethe–Slater curve leads to stronger Fe–Fe exchange interactions and enhancing ferromagnetic interactions. This work not only proposes the novel rhombohedral Y2Fe17H3.5 with excellent magnetic properties, but also provides a new method for hydrogen doping in Y2Fe17 which lays the foundation of fundamental solid state physics for further research. [ABSTRACT FROM AUTHOR]

Magnetic and magnetocaloric properties of L a 0.85 S r 0.15 M n 0.99 F e 0.01 O 3 perovskite oxides are investigated in the framework of the mean-field theory with a goal to develop a comprehensive model with parameters that can be used to optimize the caloric performances for cooling applications. Using the experimental magnetic isotherms M(H,T), we estimate and compare the exchange parameter (λ) , the saturation magnetization (M 0) , the total angular momentum (J) , and the gyromagnetic factor (g) for two different samples annealed at 1170 and 1250 °C. These parameters are used, in turn, in the simulation of the magnetic and the magnetocaloric properties of these L a 0.85 S r 0.15 M n 0.99 F e 0.01 O 3 compounds assuming imperfect samples with compositional and/or magnetic inhomogeneities. For this purpose, a Gaussian distribution of the Curie temperature is assumed. The temperature dependence of the magnetic entropy change, − Δ S M (T) , resulting from an applied field variation is simulated for both samples. The selected distribution captures the rounding of the − Δ S M (T) peak at its maximum and its broadening with growth conditions, features that are constantly observed in many bulk polycrystalline compounds. [ABSTRACT FROM AUTHOR]

In this paper, the effects of hydrostatic stress on the magnetic properties of Mn-Zn power ferrites are discussed. Ring cores were embedded in cement and the curing process gradually exerted pressure on the core. A novel testing method was developed to continuously measure the power losses and the magnetic susceptibility in dependence on magnetic excitation at a fixed frequency and room temperature with a vector network analyzer. After 450 h, a maximum compressive stress of 120 MPa was reached. Power loss up to 300% was observed, while magnetic susceptibility dropped by 35%. The magneto-mechanical effect on core losses was simulated with the Hodgdon–Esguerra hysteresis model, showing excellent agreement with tested results, which allows us to predict the behavior of ferrite tiles embedded in load-bearing surfaces for wireless power transfer (WPT) applications. [ABSTRACT FROM AUTHOR]

In this paper, we have studied the effect on the structure and magnetic properties of partial Pd substitution by Gd in Fe–Pd thin films of nominal composition Fe56Pd44−xGdx (x = 1, 3, 5, and 7), deposited onto Si(100) and Si(100)/SiO2 substrates by thermal evaporation. Several techniques contribute to the characterization of their microstructure and magnetic properties, such as x-ray diffraction (XRD), scanning electron microscopy, alternating gradient field magnetometry, and magnetic force microscopy (MFM). X-ray diffraction shows that the as-deposited films are either amorphous or contain a disordered FePd phase, depending on the film thickness. The transformation of disordered fcc-FePd into ordered fct-FePd has been induced by a heat treatment at 530 °C for 4 h. The addition of gadolinium leads to a reduction in the coercivity as a consequence of the emergence of soft phases and of the progressive reduction of the fct-FePd phase, which is primarily responsible for the observed maze magnetic domains. The exchange coupling between the soft phase and the hard fct-FePd phase is demonstrated by first-order reversal curves (FORCs). [ABSTRACT FROM AUTHOR]

Rare-earth doped materials are of immense interest for their potential applications in linear and nonlinear photonics. There is also intense interest in sub-nanometer gold clusters due to their enhanced stability and unique optical, magnetic, and catalytic properties. To leverage their emergent properties, here we report a systematic study of the geometries, stability, electronic, magnetic, and linear and nonlinear optical properties of Au5RE (RE = Sc, Y, La–Lu) clusters using density-functional theory. Several low-energy isomers consisting of planar or non-planar configurations are identified. For most doped clusters, the non-planar configuration is energetically favored. In the case of La-, Pm-, Gd-, and Ho-doped clusters, a competition between planar and non-planar isomers is predicted. A distinct preference for the planar configuration is predicted for Au5Eu, Au5Sm, Au5Tb, Au5Tm, and Au5Yb. The distinction between the planar and non-planar configurations is highlighted by the calculated highest frequencies, with the stretching mode of the non-planar configuration predicted to be stiffer than the planar configuration. The bonding analysis reveals the dominance of the RE-d orbitals in the formation of frontier molecular orbitals, which, in turn, facilitates retaining the magnetic characteristics governed by RE-f orbitals, preventing spin-quenching of rare earths in the doped clusters. In addition, the doped clusters exhibit small energy gaps between frontier orbitals, large dipole moments, and enhanced hyperpolarizability compared to the host cluster. [ABSTRACT FROM AUTHOR]

The microstructure morphology, static magnetic properties, and electromagnetic absorption characteristics of nano FexCoNi alloy particles prepared by chemical liquid deposition with five different Fe content levels are investigated in this paper. The results show that spherical FexCoNi alloy particles with an average particle size of about 100–200 nm and a face-centered cubic crystal structure were obtained. All five samples exhibited soft magnetic behavior, with the saturation magnetization intensity showing an increasing-then-decreasing trend with increasing Fe content, peaking at 141.8 emu/g for Fe content x = 1.0. The dielectric constants (real and imaginary parts) of the prepared alloy particles exhibit significant differences with respect to the variation of Fe content, while the changes in the real and imaginary parts of the magnetic permeability show less pronounced effects with increasing Fe content. As the electromagnetic wave frequency increases, the real parts of the dielectric constants for all composites show minimal fluctuations, and the real parts of the magnetic permeability exhibit a decreasing trend. Moreover, the imaginary parts of the dielectric constants and magnetic permeability show an increasing followed by a decreasing trend as the frequency rises. The material with Fe content x = 1 demonstrated optimal dielectric loss performance and relatively excellent magnetic loss performance, with a sample thickness of 1.9 mm exhibiting the highest reflection loss (RLmax) of −24.2 dB and an effective absorption bandwidth of 4.48 GHz. [ABSTRACT FROM AUTHOR]

VO2 is renowned for its electric transition from an insulating monoclinic (M1) phase, characterized by V–V dimerized structures, to a metallic rutile (R) phase above 340 K. This transition is accompanied by a magnetic change: the M1 phase exhibits a non-magnetic spin-singlet state, while the R phase exhibits a state with local magnetic moments. Simultaneous simulation of the structural, electric, and magnetic properties of this compound is of fundamental importance, but the M1 phase alone has posed a significant challenge to the density functional theory (DFT). In this study, we show none of the commonly used DFT functionals, including those combined with on-site Hubbard U to treat 3d electrons better, can accurately predict the V–V dimer length. The spin-restricted method tends to overestimate the strength of the V–V bonds, resulting in a small V–V bond length. Conversely, the spin-symmetry-breaking method exhibits the opposite trends. Each of these two bond-calculation methods underscores one of the two contentious mechanisms, i.e., Peierls lattice distortion or Mott localization due to electron–electron repulsion, involved in the metal–insulator transition in VO2. To elucidate the challenges encountered in DFT, we also employ an effective Hamiltonian that integrates one-dimensional magnetic sites, thereby revealing the inherent difficulties linked with the DFT computations. [ABSTRACT FROM AUTHOR]

Element substitution of BaTiO 3 -based compounds has been demonstrated as a powerful way for designing novel electronic materials (such as polar metals and multiferroics). To trigger magnetism into ferroelectric BaTiO 3 , general substituted elements are magnetic transition metals (such as Mn, Fe, and Co). The doping effect of rare-earth elements (such as Dy) in BaTiO 3 -based compounds was barely investigated. Here, we report the coexistence of magnetism and electric polarization in epitaxial Dy 0.5 Ba 0.5 TiO 3 films. The single-crystalline films were synthesized by high-pressure magnetron sputtering. The crystal and electronic structures were characterized by high-resolution x-ray diffraction, x-ray photoemission spectroscopy, and resonant soft x-ray absorption spectroscopy. Room-temperature electric polarization was demonstrated by optical second-harmonic generation. Temperature-dependent magnetic hysteresis loops were measured to reveal the revolution of magnetism on temperature. Surprisingly, it is uncovered that the Curie temperature of electric-polarized Dy 0.5 Ba 0.5 TiO 3 films is around 100 K, far above the critical temperature of non-polarized DyTiO 3 (near 60 K). Our work provides another view to understand the magnetoelectric materials. [ABSTRACT FROM AUTHOR]

The effect of the YBCO superconducting (SC) state on the magnetic properties of as-grown YBCO/Co/IrMn heterostructures has been systematically studied using magnetometry and ferromagnetic resonance. The obtained data showed that the superconductivity of the YBCO substrate strongly affects the ferromagnetic properties of the deposited Co layer deeper (up to 50 nm) than the coherence length of the YBCO (≃ 4 nm) by an exchange interaction between the Co magnetic moments and the superconducting pairs at the YBCO/Co interface. The interfacial exchange interaction, switched on while the YBCO enters the SC state, pins Co spins and yields an enhancement of the Co magnetic properties. [ABSTRACT FROM AUTHOR]

VO2 is renowned for its electric transition from an insulating monoclinic (M1) phase, characterized by V–V dimerized structures, to a metallic rutile (R) phase above 340 K. This transition is accompanied by a magnetic change: the M1 phase exhibits a non-magnetic spin-singlet state, while the R phase exhibits a state with local magnetic moments. Simultaneous simulation of the structural, electric, and magnetic properties of this compound is of fundamental importance, but the M1 phase alone has posed a significant challenge to the density functional theory (DFT). In this study, we show none of the commonly used DFT functionals, including those combined with on-site Hubbard U to treat 3d electrons better, can accurately predict the V–V dimer length. The spin-restricted method tends to overestimate the strength of the V–V bonds, resulting in a small V–V bond length. Conversely, the spin-symmetry-breaking method exhibits the opposite trends. Each of these two bond-calculation methods underscores one of the two contentious mechanisms, i.e., Peierls lattice distortion or Mott localization due to electron–electron repulsion, involved in the metal–insulator transition in VO2. To elucidate the challenges encountered in DFT, we also employ an effective Hamiltonian that integrates one-dimensional magnetic sites, thereby revealing the inherent difficulties linked with the DFT computations. [ABSTRACT FROM AUTHOR]

The antiferromagnetic orthoferrite YFeO3 possesses fascinating magnetic properties for spintronics, such as terahertz spin dynamics, ultrafast domain wall motion, and long magnon decay length. YFeO3 belongs to a special family of antiferromagnets that show an unusually strong non-trivial Kerr response due to its weak ferromagnetism. The highly stable antiferromagnetic domains without any spontaneous spin rotation transitions below the 645 K Néel temperature may be useful for nanoscale device applications. We report the successful fabrication of high-quality twinning-free (110)-oriented YFeO3 films by pulsed laser deposition. Detailed structural and magnetic characterization revealed that the crystal structure and magnetic properties of the YFeO3 films are comparable to bulk single crystals. We show that the spin rotation under high magnetic fields follows the two-sublattice approximation model. The film surface is atomically flat with step-terrace surface morphology. A longitudinal magneto-optic Kerr (MOKE) rotation of 10 mdeg was observed at room temperature, which is consistent with earlier reports on bulk single crystals. The in-plane anisotropy of the Kerr response corresponds to the obtained magnetic anisotropy from the SQUID measurement. The large MOKE signal enables the imaging of antiferromagnetic domains and their reversal. The domain size was found to be larger than 100 μm. These high-quality YFeO3 thin films facilitate the fabrication of antiferromagnetic spintronic devices and provide a convenient platform for studying various spin-related phenomena in thin films and at interfaces. [ABSTRACT FROM AUTHOR]

Binary kagome compounds TmXn (T = Mn, Fe, Co; X = Sn, Ge; m:n = 3:1, 3:2, 1:1) have garnered recent interest owing to the presence of both topological band crossings and flatbands arising from the geometry of the metal-site kagome lattice. To exploit these electronic features for potential applications in spintronics, the growth of high-quality heterostructures is required. Here, we report the synthesis of Fe/FeSn and Co/FeSn bilayers on Al2O3 substrates using molecular beam epitaxy to realize heterointerfaces between elemental ferromagnetic metals and antiferromagnetic kagome metals. Structural characterization using high-resolution x-ray diffraction, reflection high-energy electron diffraction, and electron microscopy reveals that the FeSn films are flat and epitaxial. Rutherford backscattering spectroscopy was used to confirm the stoichiometric window where the FeSn phase is stabilized, while transport and magnetometry measurements were conducted to verify metallicity and magnetic ordering in the films. Exchange bias was observed, confirming the presence of antiferromagnetic order in the FeSn layers, paving the way for future studies of magnetism in kagome heterostructures and potential integration of these materials into devices. [ABSTRACT FROM AUTHOR]

The capacity to externally manipulate magnetic properties is highly desired from both fundamental and technological perspectives, particularly in the development of magnetoelectronics and spintronics devices. Here, using first-principles calculations, we have demonstrated the ability of controlling the magnetism of magnetized graphene monolayers by interfacing them with a two-dimensional ferroelectric material. When the 3d transition metal (TM) is adsorbed on the graphene monolayer, its magnetization easy axis can be flipped from in-plane to out-of-plane by the ferroelectric polarization reversal of In2Se3, and the magnetocrystalline anisotropy energy (MAE) can be high to −0.692 meV/atom when adopting the Fe atom at bridge site with downward polarization. This may be a universal method since the 3d TM-adsorbed graphene has a very small MAE, which can be easily manipulated by the ferroelectric polarization. As a result, the inherent mechanism is analyzed by the second variation method. [ABSTRACT FROM AUTHOR]

The capacity to externally manipulate magnetic properties is highly desired from both fundamental and technological perspectives, particularly in the development of magnetoelectronics and spintronics devices. Here, using first-principles calculations, we have demonstrated the ability of controlling the magnetism of magnetized graphene monolayers by interfacing them with a two-dimensional ferroelectric material. When the 3d transition metal (TM) is adsorbed on the graphene monolayer, its magnetization easy axis can be flipped from in-plane to out-of-plane by the ferroelectric polarization reversal of In2Se3, and the magnetocrystalline anisotropy energy (MAE) can be high to −0.692 meV/atom when adopting the Fe atom at bridge site with downward polarization. This may be a universal method since the 3d TM-adsorbed graphene has a very small MAE, which can be easily manipulated by the ferroelectric polarization. As a result, the inherent mechanism is analyzed by the second variation method. [ABSTRACT FROM AUTHOR]

Magnetic refrigeration technology is regarded as one of the ideal solutions for cryogenic refrigeration, while magnetocaloric materials are the crucial ones. A series of polycrystalline RE2Ti2O7 (RE = Gd, Tb, and Ho) compounds were prepared by a simple one-step solid-phase reaction method in the atmosphere. The crystal structure, magnetic properties, and magnetocaloric effect (MCE) of these compounds were systematically investigated. Crystallographic research indicates that these compounds crystallized in a pyrochlore structure. Meanwhile, magnetic measurements illustrate that this class of pyrochlore oxides is highly frustrated magnetic materials and exhibits complex magnetic behavior. In addition, under the field change of 0–1 T, the values of the maximum magnetic entropy change (− Δ S M max ) and the refrigeration capacity are calculated to be 0.9 and 5.8 J/kg for Gd2Ti2O7, 9.0 and 32.9 J/kg for Tb2Ti2O7, 9.9 and 29.9 J/kg for Ho2Ti2O7, respectively. Therefore, RE2Ti2O7 (RE = Tb and Ho) pyrochlores exhibit excellent MCEs under low magnetic fields, providing candidate materials for the application of cryogenic magnetic refrigeration technology. [ABSTRACT FROM AUTHOR]

The realization of remarkable thermoelectric (TE) properties in a novel single-crystalline quantum material is a topic of prime interest in the field of thermoelectricity. It necessitates a proper understanding of transport properties under magnetic field and magnetic properties at low field. We report polarized Raman spectroscopic study, TE properties, and magneto-resistance (MR) along with magnetic characterization of single-crystalline Bi2Se3. Polarized Raman spectrum confirms the strong polarization effect of A 1 g 1 and A 1 g 2 phonon modes, which verifies the anisotropic nature of the Bi2Se3 single crystal. Magnetization measurement along the in-plane direction of single crystal divulges a cusp-like paramagnetic response in susceptibility plot, indicating the presence of topological surface states (TSSs) in the material. In-depth MR studies performed in different configurations also confirm the presence of anisotropy in the single-crystalline Bi2Se3 sample. A sharp rise in MR value near zero magnetic field and low-temperature regime manifests a weak anti-localization (WAL) effect, depicting the quantum origin of the conductivity behavior at low temperature. Moreover, in-plane magneto-conductivity data at low-temperature (up to 5 K) and low-field region (≤15 kOe) confirm the dominance of the WAL effect (due to TSS) with a negligible bulk contribution. Quantum oscillation (SdH) in magneto-transport data also exhibits the signature of TSS. Additionally, an exceptional TE power factor of ∼950 μW m−1 K−2 at 300 K is achieved, which is one of the highest values reported for pristine Bi2Se3. Our findings pave the way for designing single crystals, which give dual advantages of being a good TE material along with a topological insulator bearing potential application. [ABSTRACT FROM AUTHOR]

Magnetic garnet thin films exhibiting perpendicular magnetic anisotropy (PMA) and ultra-low damping have recently been explored for applications in magnonics and spintronics. Here, we present a systematic study of PMA and magnetic damping in bismuth-substituted yttrium iron garnet (Bi-YIG) films grown on sGGG (111) substrates by pulsed laser deposition. Films with thicknesses ranging from 5 to 160 nm are investigated. Structural characterization using x-ray diffraction and reciprocal space mapping demonstrates the pseudomorphic growth of the films. The films exhibit perpendicular magnetic anisotropy up to 160 nm thickness, with the zero-magnetic field state changing from fully saturated for low thicknesses to a dense magnetic stripe pattern for thicker films. The films show a ferromagnetic resonance (FMR) linewidth of 100–200 MHz with a Gilbert damping constant of the order of 4 × 10 − 3 . The broad FMR linewidth is caused by inhomogeneities of magnetic properties on micrometer length scales. [ABSTRACT FROM AUTHOR]

Spherical powders are required for many advanced manufacturing techniques due to their inherent requirement of flowability, either within feed tubes or during powder spreading. As advanced manufacturing of magnets continues to develop, new production methods for feedstocks are also sought. Plasma spheroidization is a high-yield method to produce spherical Nd–Fe–B powders from irregularly shaped particles, with advantages including high throughput and a well-controlled size distribution. Highly spherical Nd–Fe–B powders with large scale production (i.e., kg) have been demonstrated using an inductively coupled thermal plasma system; however, the magnetic properties of the output powder display significant degradation. The coercivity was decreased from the initial 8 kOe (636 kA/m) of the as-received to 0.7 kOe (55 kA/m) for spheroidized powders. Microstructural investigation reveals 6% Nd depletion caused by the extreme temperatures of the plasma, leading to the formation of low-coercivity α-Fe and a subsequent decrease in energy product. Post-spheroidization heat treatments with Nd can partially mitigate the coercivity degradation, increasing to 1.7 kOe (135 kA/m), potentially offering a pathway toward spherical powders for a range of applications. [ABSTRACT FROM AUTHOR]

We study epitaxial growth, crystal structures, and magnetic properties of Fe–As compound thin films grown on GaAs (111)B substrates at various values of the As4:Fe flux ratio γ, using molecular beam epitaxy. The samples grown at low As4 flux (γ = 0.3, sample A) show mainly a body-centered-cubic (bcc) crystal structure, exhibiting ferromagnetic properties similar to bcc Fe. Meanwhile, the Fe–As samples grown at medium γ (2.7–4.5, sample group B) comprise regions of Ni2In-type FeAs (a hexagonal crystal with lattice constants of a = 0.399 nm and c = 0.536 nm), which are grown at the bottom and interface with the GaAs buffer layer, and a layer of non-stoichiometric FeAs with a DO3 structure (a = 0.522 nm) formed on the top. The DO3-structure FeAs phase contains partially transformed regions, which are characterized by thin stripes in a scanning transmission electron microscopy image. Furthermore, in the sample grown with high γ = 8.5 (sample C), a hexagonal Fe–As crystal with a large in-plane lattice constant (a = 0.691 nm and c = 0.542 nm) and threefold screw axes are observed. None of these crystal structures of Fe–As compounds has ever been reported. While sample C shows no ferromagnetism, the samples in group B exhibit strong ferromagnetism with high Curie temperature TC above 400 K. These new ferromagnetic Fe–As compounds are promising for spintronic device applications. [ABSTRACT FROM AUTHOR]