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This work explores two key areas in the study of van der Waals heterostructures: their utilization in developing quantum tunneling devices and the observation of time-reversal symmetry breaking within superconductors.In the first part, the research focuses on Quantum tunneling devices utilizing van der Waals heterostructures. These devices have garnered significant attention due to their ability to elucidate the nature of quasi-particle excitations and energy states through inelastic electron tunneling spectroscopy (IETS). Specifically, graphite-based tunnel junctions with insulating barriers like hexagonal boron nitride (h-BN) are pivotal in understanding quantum phenomena in non-magnetic tunnel junctions. Recent device-oriented studies on magnetic tunnel junctions indicate that Landau levels and magnon excitations play a role when electrons tunnel between graphite layers. However, to thoroughly investigate the tunneling mechanisms involving Landau levels and excitations, a comprehensive study involving magnetic field and temperature dependencies through IETS is essential. In this context, we fabricated tunnel junction devices with graphite electrodes and thin h-BN/MoS2 as insulating barriers, conducting extensive transport measurements. Our low-temperature findings revealed trivial phonon excitations without signs of magnon or Landau levels in these non-magnetic tunnel junctions. This study aims to understand quasiparticle behavior and spin-polarized Landau levels for enhancing the performance and reliability of magnetic tunnel junctions (MTJs), with applications in spintronics and quantum sensing.In the second part, we move beyond the proximity effect to the direct study of time-reversal symmetry breaking in superconductors intrinsically, where van der Waals heterostructures have shown significant potential for applications involving stacking and twisting of layers. Concurrently, Iron-based d-wave superconductors have been realized to exhibit topological surface superconductivity. However, previous studies have predominantly been restricted to bulk characterizations and lack comprehensive device-oriented investigations. Here, for the first time, we demonstrate the evolution of symmetry breaking coexisting with superconductivity at the interface of twisted thin van der Waals Iron Selenide Josephson Junctions. A post-fabrication free approach for ultra-clean interface has been implemented. Twisting the bottom layer approximately 6 degrees in the vertically stacked Junction has displayed the emergence of ferromagnetism in addition to superconducting d-wave symmetry below the critical temperature. Further, the current trainable sequence by modulating the Josephson phase particle between the two superconducting degenerate ground states confirmed the spontaneous time-reversal symmetry breaking in the system.

Topological antiferromagnets have a significant role to play in the modern day electronics and spintronics due to the presence of peculiar symmetries and magnetically driven large anomalous transport behaviour. We report the observation of anomalous Hall effect in Mn3Sn polycrystalline thin films deposited on Al2O3 substrate with a large anomalous Hall conductivity of 65 (Ωcm)−1 at 3 K. The Hall and magnetic measurements show a very small hysteresis owing to a weak ferromagnetic moment present in this material. The longitudinal resistivity decreases sufficiently for the thin films as compared to the polycrystalline bulk sample used as the target for the film deposition. The anomalous Hall resistivity and conductivity decreases almost linearly with the increase in the temperature. A negative magnetoresistance is observed for all the measured temperatures with the negative decrease in the magnitude with the increase in temperature.

We investigated the growth and electronic properties of Co-phthalocyanine (CoPc) molecule deposited on iron film with different structures (pseudomorph-fcc and bcc) and on iron nanowires by scanning tunnelling microscopy and X-ray absorption spectroscopy (XAS). CoPc molecules self-assemble in a two-dimensional (2D) arrangement with the molecular plane parallel to the iron surfaces, and the local order is lost after the first layer. The molecule ferromagnet interaction causes the broadening of Co and N unoccupied molecular states as well as different electronic distribution of N states as a function of the atomic structure of iron surface. The ferromagnetic coupling between the molecule and the iron film is dominated by the electronic interaction between Co and the first Fe layer. CoPc 2D arrangement turns into 1D by using as a template the iron nanowire grown on a facet surface of oxidized Cu(332) surface. CoPc molecules interact weakly with the iron nanowires manifesting a substantial Co 3d(z) spectral feature in XAS spectrum and the possibility of a magnetic interaction between Co moment and iron nanowires. Both CoPc 2D and 1D arrangements can open up new interesting scenarios to tune the magnetic properties of hybrid interfaces involving metallorganic molecules.

A new ternary Mg1.4Co21.6B6 compound in the Mg-Co-B system was synthesized via a conventional solid-state reaction method and the effect of Ni-substitution on its crystal structure, thermal stability, solid solubility and physical properties were systematically investigated. The crystal structure of the Mg1.4Co21.6B6 compound was fully determined by the X-ray diffraction technique with Rietveld refinement method. It is found that Mg1.4Co21.6B6 crystallizes in the form of C6Cr23 structure type (space group: Fm-3m (No.225), a = 10.556(1)A, Z = 4). The results showed that the 4a sites have been occupied completely by Co atoms in present compound which with M2-xNi21+xB6 form belonging to the W2Cr21C6-type. When Mg1.4Co21.6B6 is repeatedly sintered at elevated temperatures, it becomes unstable and decomposes into Co3B and Mg. The lattice parameters of the Mg1.4Co21.6B6 solid solution alters dramtically with increasing Ni substitution, with no regular trend being observed. The electrical and magnetic performances of the 3.6Mg:3Co:17Ni:6B and 3.6Mg:3Co:18Ni:6B (nominal compositions) samples suggest that both samples are typical ferromagnetic materials. The temperature in the maximum drop of the ρ(T) curve decreases as a function of the Ni content. Base on the correlation between the critical temperature and Ni content, a linear fitting equation is obtained and the critical temperature of Mg1.4Co21.6B6 calculated utilizing the linear fitting equation. The findings in this work may provide certain reference values for material science on electrical magnetic properties and other references for researching the material further.

In this paper, the effect of Ba2+ ions A-site doping LaFeO3 on structure, magnetic properties and microwave absorption properties was investigated by the sol-gel method. According to the TEM and FullProf refinement results, the structure of LaFeO3 changes from orthogonal (SG: Pnma) to cubic (SG: Pm-3m) when the Ba doping amount is x = 0.4. The SEM image shows that the particles size tends to decrease with the increase of Ba content. The production of weak ferromagnetism indicates that Ba doping has a significant effect on the magnetic properties of LaFeO3. The Neel temperature (TN) decreases significantly with the increase of Ba doping amount. An appropriate amount of Ba doping can effectively increase the dielectric and magnetic loss of LaFeO3 ceramics powders. The increase permittivity (e′) may have been attributed to the hopping spin of the electrons between the Fe3+ and Fe4+ ions with the Ba2+ ions doping. The minimum reflection loss (RL) of La0.9Ba0.1FeO3 at 6.72 GHz reached –30.04 dB, its effective bandwidth (RL ≤ –10 dB) is 2.1 GHz, and the matching thickness is only 3.2 mm. These results indicate that Ba doping can effectively control the microwave absorption properties of LaFeO3, especially in the C-band.

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Van der Waals (vdW) magnets provide an exciting opportunity for exploring two-dimensional (2D) magnetism for next generation scientific and technological advances. While previously realized in 3D ultrathin films where the magnetism is stabilized via substrate-assisted magnetic anisotropy, recent reports have shown intrinsic ferromagnetism at low temperatures (< 60 K) in isolated µm-sized flakes mechanically exfoliated from a bulk single-crystal down to a single-atomic layer. This opens up the possibility to truly study magnetism in free-standing 2D layers without direct effects from the underlying substrate and being intrinsically susceptible to surface effects such as atomic adsorbates, electrostatic gating, and proximity-induced phenomena. This dissertation examines the molecular beam epitaxy (MBE) growth and characterization of new 2D magnets, monolayers of MnSe2 and VSe2, that show ferromagnetic ordering above room temperature. Growth on different substrates and varying the substrate temperature during growth affects the growth mode and morphology of the deposited 2D magnet and also affects the measured magnetization. Direct atomic and magnetic imaging via scanning transmission electron microscopy (STEM) and scanning tunneling microscopy (STM) show stable 2D magnetic layers.Due to the lack of dangling bonds at the surface of these 2D magnets, applying external epitaxial strain is a challenge. Later in this dissertation, the magnetic, electronic, and structural properties of vdW-layered, Fe-deficient Fe3−xGeTe2 are systematically investigated by he application of high pressure. Fe3GeTe2 is of particular interest due to its high Curie temperature, Tc, strong perpendicular magnetic anisotropy, and tunable magnetic properties depending on the concentration of Fe and its thickness. Electrical and magneto-transport measurements show a suppression in Tc with an increasing pressure up to 20 GPa. The decrease in Tc is due to the lattice shrinkage from pressurization which leads to a weakening of the exchange interaction. These observations showcase the tunability in vdW magnets via pressure which can complement other external stimuli such as chemical doping, making them candidates for future spintronic, electronic and photonic devices.

Developing novel magnetocaloric materials is of great significance for the applications of magnetic refrigeration. In this study, we designed a heterogeneous rare-earth-based high-entropy alloy (HEA) comprising amorphous matrix, local crystal-like cluster and nanocrystalline dihydride with average size of 7.5 nm through isothermal hydrogenation. This heterogeneous structure can significantly tune the magnetocaloric effect of alloy. After hydrogenation, the predominant exchange interaction transforms from ferromagnetic to antiferromagnetic with the disappearance of spin-glass-like behavior, and a complete second-order magnetic transition is obtained. Compared with the Gd20Tb18Dy18Co20Al24 high-entropy metallic glass with a small number of nanocrystals, the maximum magnetic entropy change of the hydrogen-containing HEA is increased from 8.8 to 13.6 J kg−1 K−1 under applied magnetic field change of 5 T accompanying unobvious hysteresis and decreased magnetic transition temperature from 59 to 8 K, which is more promising as magnetic refrigerant at cryogenic temperature. This work provides a novel concept of designing heterogeneous structure in terms of special cluster and preferential nanocrystalline to modulate the properties of metallic glasses.

Magnetism has revolutionized important technologies, and continues to bring forth new phenomena in emergent materials and reduced dimensions. Here, using first-principles calculations, we demonstrate that the already-synthesized two-dimensional (2D) Ni-tetracyanoquinodimethane (Ni2(TCNQ)2) lattice is a stable ferromagnetism material with multiple spin-polarized Dirac cones. The conical bands in proximity of the Fermi level can be tuned by external tensile strain and show the fourfold degenerate electronic states at the critical tensile strain of ∼2.35%, whose energy dispersion is consistent with 2D Cairo pentagonal lattice. In addition, spin-orbital coupling can open a band gap at the Dirac point of A, leading to topologically nontrivial electronic states characterized by the non-zero Chern number and the edge states of nanoribbon. Our results offer versatile platforms for the realization of massless spintronics with full-spin polarization in 2D Cairo pentagonal Ni2(TCNQ)2 Lattice.

In this paper, we systematically investigated the microstructure evolution and coercivity mechanism of hydrogenation-disproportionation-desorption-recombination (HDDR) treated Nd-Fe-B strip cast alloys by transmission electron microscopy (TEM) and three-dimensional atom probe (3DAP) analyses. The rod-like NdH2+x phases with diameters of 10–20 nm are embedded into α-Fe matrix, which hereditarily leads to textured grains in HDDR alloy. The migration of NdH2+x from Nd-rich region to α-Fe matrix during hydrogen absorption process contributes to the uniform redistribution of Nd-rich phases after HDDR treatment. The HDDR alloy with single domain grain sizes of 200–300 nm exhibits relatively low coercivity of 1.01 T that arises from pinning magnetic domain motion. The weak c-axis orientation of HDDR alloy results in a lower reverse magnetic field (coercivity) to reduce remanence to 0. Moreover, the direct contact of Nd2Fe14B grains and the high concentration of ferromagnetic elements (Fe content ≈ 66.06 at%, Co content ≈ 0.91 at%) in Nd-rich grain boundary layer lead to strong magnetostatic coupling effect among Nd2Fe14B grains. The nano-sized α-Fe inside Nd2Fe14B matrix makes the magnetization reversal easily and decreases the coercivity of HDDR alloy.

The topological insulator BiSb is promising for spin-orbit torque applications thanks to its high electrical conductivity and giant spin Hall effect. Previous works have reported a large spin Hall angle for BiSb deposited on top of a ferromagnetic layer (FM) with perpendicular magnetic anisotropy. However, since BiSb has large surface roughness, obtaining a large spin Hall angle in BiSb (bottom)/FM is more challenging than in FM/BiSb(top) structures, especially when the FM layer is very thin. Here, we investigate the role of an interfacial layer on the effective spin Hall angle in BiSb (bottom)/FM with in-plane magnetization deposited by magnetron sputtering on sapphire substrates. We showed that inserting an interfacial layer with optimized thickness helps improve the effective spin Hall angle. We achieved a relatively high effective spin Hall angle of 1.7 in BiSb (bottom)/Ru 1 nm/ Co 1 nm/ Pt 1 nm structure.

Half-metallic Heusler alloys typically have in-plane magnetic anisotropy, which can be converted to perpendicular by attaching MgO or heavy metal, e.g., Pt, layers as similarly applied for conventional ferromagnets. Recently we have found body-centered cubic (bcc) seed layers, e.g., V and W, to induce perpendicular anisotropy in Heusler-alloy films above, however, they show small giant magnetoresistive (GMR) ratios in spin-valve structures to date. This is partially because of the large resistivity of the seed layer and the nonmagnetic layer in the spin-valve. In this study, we have systematically investigated nonmagnetic overlayers and have found that a Ag layer best maintains the perpendicular anisotropy. The corresponding GMR devices have then been fabricated and characterized, achieving the GMR ratio of ~0.03% at room temperature. Such bcc seed layers can offer an alternative method for perpendicularly magnetized GMR junctions for applications.

The table-like magnetocaloric effect is significant for the magnetic refrigeration applications above 20 K based on the Ericsson cycle. Herein, we prepared a series of Nd6Fe13Pd1–xCux (x=0.05, 0.1, 0.15) compounds by the arc-melting method. These compounds show the single crystalline phase in the tetragonal Nd6Fe13Si-type structure with the space group I4/mcm. A magnetic phase transition from ferromagnetism to antiferromagnetism and a metamagnetic transition from the antiferromagnetic state to the ferromagnetic state were observed in each of the compounds. The compounds exhibit table-like magnetocaloric effects with large refrigerant capacities. A constant ΔSM in a temperature span of 40 K in the Nd6Fe13Pd0.85Cu0.15 compound was observed. For a field change of 0–5 T, the peak values of –ΔSM for the Nd6Fe13Pd0.95Cu0.05, Nd6Fe13Pd0.90Cu0.10, and Nd6Fe13Pd0.85Cu0.15 compounds were estimated to be 4.8, 4.6 and 4.4 J/(kg·K) with corresponding refrigerant capacity values of 323, 331 and 316 J/kg, respectively. The obtained table-like magnetocaloric effects with large refrigerant capacities as well as fairly small thermal and magnetic hysteresis deem these series of compounds good candidates for single-phase magnetic refrigeration based on the Ericsson cycle.

Structural, optical and magnetic properties are reported for new synthesized perovskite materials. Ba0.3La0.7Ti0.3Fe0.7O3 and Ba0.1La0.9Ti0.1Fe0.9O3 compositions were prepared via solid state reaction. X-ray analysis confirms that both compositions show feature of perovskite structure. Rietveld refinement method was used to confirm the phase formation and investigate the structure and space group. The study demonstrates the formation of orthorhombic structure with Pnma space group for Ba0.3La0.7Ti0.3Fe0.7O3 while the composition Ba0.1La0.9Ti0.1Fe0.9O3 structure adopts Pbnm symmetry. UV-vis spectroscopy measurements show very broad and intense UV-visible light absorption, the estimated band gap ranges between 2.07 and 2.15 eV. Magnetic measurements were carried out for the compositions Ba0.3La0.7Ti0.3Fe0.7O3 and Ba0.1La0.9Ti0.1Fe0.9O3. The hysteresis loop of both samples at 300 and 10 K show a strong ferromagnetic behavior. The temperature dependent magnetization at 0.05 T under field-cooled (FC) and zero field cooled (ZFC) modes shows magnetic frustration or spin glass-like behavior.

Revealing the magnetic coupling nature of boundary defects is crucial for in-depth understanding of the behavior and properties of magnetic materials and devices. Here, magnetite (i.e., Fe3O4) thin films were grown epitaxially on (100) SrTiO3 single-crystal substrates by pulsed laser deposition. Atomic-scale scanning transmission electron microscopy characterizations reveal that three types of antiphase boundaries (APBs) are formed in the Fe3O4 thin film. They are the (100) APB that is formed on the (100) plane with a crystal translation of (1/4)a[01 1 ¯ ], the type I and type II (110) APBs that are both formed on the (110) plane with the same crystal translation of (1/4)a[101] but different terminated atomic planes. The type I (110) APB is terminated at the atomic plane with mixed tetrahedral- and octahedral-sites Fe atoms, the type II (110) APB is terminated at the octahedral-site Fe plane. First-principles calculations reveal that the (100) APB and the type I (110) APB tend to form the ferromagnetic coupling that will not decrease the spin polarization of Fe3O4 films, while the type II (110) APB prefers to form the antiferromagnetic coupling that will degrade the magnetic properties. The magnetic coupling modes of the APBs are closely related to the Fe-O-Fe bond angles across the boundaries.

Fluxgate magnetometers provide sensitive and stable measurements of the static and low frequency vector magnetic field. Fluxgates form a magnetic field measurement by periodically saturating a ferromagnetic core and the intrinsic magnetic noise of this material can determine the noise floor of the instrument. We present the results of an empirical experiment to understand the physical parameters that influence the intrinsic magnetic noise of fluxgate cores. We compare two permalloy alloys – the historical standard 6 % molybdenum alloy and a new 28 % copper alloy. We examine the influence of geometry using the historical standard 1” diameter spiral wound ring-core and a new stacked washer racetrack design. We evaluate the influence of material thickness by comparing 100 µm and 50 µm foils. Finally, we investigate heat treatments in terms of temperature and ramp rate and their role in both grain size and magnetic noise. The results of these experiments suggest that thinner foils, potentially comprising the copper alloy, manufactured into continuous racetrack geometry washers may provide excellent performance in fluxgate sensors.

Deformation mechanisms and magnetic properties of medium and high entropy alloys (MEA/HEAs) closely relate to lattice distortion and are strongly temperature-dependent, in particular, at low temperature ranges. However, little attention has been paid to the evolution of lattice distortion with temperature decreasing and its effects on deformation behavior and magnetic state transition. In this work, we carry out in situ synchrotron radiation based X-ray powder diffraction (SR-XRD) experiments from 293 to 123 K aiming for determining lattice distortion evolutions of CrCoNi MEA, CrFeCoNi and CrMnFeCoNi HEAs. Magnetic measurements at corresponding low temperatures and cryogenic ranges are further conducted. The in situ SR-XRD results demonstrate a general reduction of lattice distortion magnitude with temperature decreasing, which shows a similar tendency with that of reported stacking fault energy (SFE) values. It is thus suggested that lattice distortion reduction possibly makes a critical contribution to deformation mechanism transition. The magnetic measurement results show a clear ferromagnetic transition of CrFeCoNi HEA when temperature is below 173 K. While, no obvious magnetic state transition is observed for CrCoNi MEA and CrMnFeCoNi HEA. The present findings on lattice distortion evolutions will pave the way for designing targeted HEAs with particular properties.

BaTiO3 ceramics doped with double perovskite Sr2KMoO6 (BT-SKM) are fabricated via solid-state reaction technology. The effects of SKM dopants on the structure, band gap and electrical/magnetic properties of BT are systematically studied. XRD and Raman spectra analysis show polycrystalline perovskite structure of the samples, which confirms the structural changes. With the addition of SKM dopants, the grain size of the samples decreases significantly. The band gaps of doped BT samples reduce, and the minimum band gap of BT-SCM is 1.77 eV, which is apparently reduced compared with the band gap of pure BT of 3.22 eV. However, the ferroelectric properties are weakened in samples doped with SKM. This ascribes to the introduction of more oxygen vacancies by dopants, which impedes the switching of domains, resulting in deterioration of ferroelectric properties. Furthermore, ferromagnetism of BT-SNM is observed, which may be attributed to the long-range exchange interaction between Ni2+ ions and oxygen vacancies. These results reveal the potential applications of these perovskite oxides in photovoltaic and memory devices.

Long-range ferromagnetic ordering in semiconductors has become an attractive research hotspot due to its promising potential in spintronics and information technology. Especially the appearance of carbon-based semiconductors represented by graphdiyne (GDY) makes it easy to realize ferromagnetic semiconductors. Herein, a convenient and effective route has been developed to prepare GDY-based magnetic semiconductors using the modification with transition metal elements including Fe, Co, and Ni, respectively. Among them, lightly doped GDY with Co (Co-GDY) exhibits the most outstanding ferromagnetism with a typical Curie's temperature above room temperature. Meanwhile, the coercive field Hc = 78 Oe at T = 300 K of Co-GDY is the smallest, demonstrating characteristics of easy magnetization. Subsequent spin-polarized DFT calculation results reveal that the robust ferromagnetism of Co-GDY arises from the most significant local magnetic moment. Significantly, a noticeable band gap can still be maintained due to the very light doping level. These results reveal an optimization strategy for selecting doping elements, promoting carbon-based semiconductors application in spin-related fields.

To investigate the influence of the addition of Pr–Ga alloys on magnetic properties and morphology of materials, the hot-deformed PrNd-Fe-B magnets were prepared by the addition of Pr–Ga alloys using a dual-alloys diffusion. The room-temperature coercivity of the hot-deformed PrNd-Fe-B magnets increases substantially from 1.68 to 2.34 T, while the remanence decreases from 1.42 to 1.24 T, by the addition of 5 wt% Pr–Ga alloys. Moreover, the thermal stability of coercivity improves from −0.46%/oC to −0.42%/oC. Two types of grain boundary phases (PrNd-rich and PrNd-Ga-rich) are generated at grain boundaries by microstructural analysis, resulting in the decrease of Fe element concentration from more than 60% to about 10% at grain boundaries. The decrease of ferromagnetic element concentration at grain boundaries and the refinement of grain are considered to be the main reasons for the improvement of coercivity and thermal stability.

Summary Single-molecule magnets (SMMs) are molecules that can retain magnetic polarization in the absence of an external magnetic field and embody the ultimate size limit for spin-based information storage and processing. Multimetallic lanthanide complexes lacking magnetic exchange coupling enable fast relaxation pathways that attenuate the full potential of these species. Employment of diamagnetic heavy main group elements with diffuse orbitals may lead to unprecedented strong coupling. Herein, two bismuth-cluster-bridged lanthanide complexes, [K(THF)4]2[Cp∗2Ln2Bi6] (Cp∗ = pentamethylcyclopentadienyl; 1-Ln, Ln = Tb, Dy), were synthesized via a solution organometallic approach. The neutral [Ln2Bi6] heterometallocubane core features lanthanide centers that are bridged by a rare Bi66− Zintl ion, which supports strong ferromagnetic interactions between lanthanides. This affords the rare observation of magnetic blocking and open hysteresis loops for superexchange-coupled SMMs comprising solely lanthanide ions. Both compounds constitute the first SMMs containing bismuth donors paving the way for promising synthetic targets for quantum computation.

Magnetocaloric materials undergoing reversible phase transitions are highly desirable for magnetic refrigeration applications. (Mn,Fe)(2)(P,Si) alloys exhibit a giant magnetocaloric effect accompanied by a magnetoelastic transition, while the noticeable irreversibility causes drastic degradation of the magnetocaloric properties during consecutive cooling cycles. In the present work, we performed a comprehensive study on the magnetoelastic transition of the (Mn,Fe)(2)(P,Si) alloys by high-resolution transmission electron microscopy, in situ field- and temperature-dependent neutron powder diffraction as well as density functional theory calculations (DFT). We found a generalized relationship between the thermal hysteresis and the transition-induced elastic strain energy for the (Mn,Fe)(2)(P,Si) family. The thermal hysteresis was greatly reduced from 11 to 1 K by a mere 4 at.% substitution of Fe by Mo in the Mn1.15Fe0.80P0.45Si0.55 alloy. This reduction is found to be due to a strong reduction in the transition-induced elastic strain energy. The significantly enhanced reversibility of the magnetoelastic transition leads to a remarkable improvement of the reversible magnetocaloric properties, compared to the parent alloy. Based on the DFT calculations and the neutron diffraction experiments, we also elucidated the underlying mechanism of the tunable transition temperature for the (Mn,Fe)(2)(P,Si) family, which can essentially be attributed to the strong competition between the covalent bonding and the ferromagnetic exchange coupling. The present work provides not only a new strategy to improve the reversibility of a first-order magnetic transition but also essential insight into the electron-spin-lattice coupling in giant magnetocaloric materials. (C) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

We report the magnetovolume effect of quaternary Heusler alloy CoFeCrAl as a potential candidate of spin gapless semiconductor. The crystal structure of CoFeCrAl was confirmed as the single phase of the ordered LiMgPdSn-type structure. From magnetization measurements at ambient pressure, the Curie temperature TC and the spontaneous magnetization Ms were determined to be 575.2 K and 2.01 μ B/f.u., respectively. The TC is higher enough than room temperature and the Ms follows the Slater-Pauling rule. High-pressure magnetization measurements showed that the Ms is almost independent of applying pressures not only at 10 K but also up to 300 K, exhibiting that the electronic state of CoFeCrAl is fully spin polarized and it is preserved even at 300 K. The experimental results reveal that the quaternary Heusler alloy CoFeCrAl is an attractive material for functional electrode ferromagnets in spintronics devices.

Exchange bias is a complex interface phenomenon often used in multiple applications ranging from magnetic field sensors to spintronics and neuromorphic computing for inducing a unidirectional anisotropy in a ferromagnetic layer exchange coupled to an antiferromagnetic layer. Despite the significant progress in understanding mechanisms behind the exchange bias, predicting and optimizing hysteresis properties of the pinned layer in real-life systems with complex crystalline and magnetic structure is still a challenge. In this work we use a combined machine learning and micromagnetic simulation approach for building a unified predictive model giving macroscopic hysteresis properties of the pinned layer for a given set of magnetic and structural parameters. The approximator can be considered as an unknown function, which can be used for finding local or global extrema for coercivity or exchange bias field. We believe that a similar approach can be applied to other computer models or high-quality experimental data for advanced analysis of functional dependencies of hysteresis properties as well as evaluation of computer model used for simulation. A machine learning model of a bilayer with exchange bias could be helpful for decreasing the computation time, optimizing layers materials and parameters, and minimizing the number of test samples.

High-entropy alloys are characteristic of extensive atomic occupational disorder on high-symmetric lattices, differing from traditional alloys. Here, we investigate the magnetic and thermal transport properties of the prototype face-centered-cubic high-entropy alloy CrMnFeCoNi by combining physical properties measurements and neutron scattering. Direct-current and alternating-current magnetizations measurements indicate a mictomagnetic behavior with coexisting antiferromagnetic and ferromagnetic interactions below room temperature and three anomalies are found at about 80, 40, and 20 K, which are related to the paramagnetic to antiferromagnetic transition, the antiferromagnetic to ferromagnetic transition, and the spin freezing, respectively. The electrical and thermal conductivities are significantly reduced compared to Ni, and the temperature dependence of lattice thermal conductivity exhibits a glass-like plateau. Inelastic neutron scattering measurements suggest weak anharmonicity so that the thermal transport is expected to be dominated by the defect scattering.

Recent advances in flexible electronic devices have stimulated demands for the fabrication of multifunctional materials on highly flexible substrates. However, flexible diluted magnetic semiconductor films have been inadequately reported thus far. In this study, I grew polycrystalline manganese (Mn)-doped indium oxide (In2O3) films on flexible mica substrates at three deposition temperatures (Td) using the pulsed laser deposition method. All the investigated Mn-doped In2O3 films exhibited high optical transparency, high electrical conductivity, room-temperature ferromagnetism, and excellent mechanical durability. The present experimental results demonstrate that Td considerably influences the optical, electrical, and magnetic properties as well as the mechanical durability of the flexible Mn-doped In2O3 films. Based on the robustness of inorganic mica at high deposition temperatures, this detailed investigation provides a strategy for fabricating flexible diluted magnetic semiconductor films, the properties of which could be carefully optimized by widely varying the Td.

Polycrystalline, MgCu2-type multicomponent Laves phase intermetallic compound Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Al2 (Cubic, space group Fd-3m, cF24) orders ferromagnetically at 80 K (TC). The TC is found to be approximately equal to the average of ferromagnetic transition temperatures of the individual components RAl2 (R = Gd, Tb, Dy, Ho and Er). Heat capacity shows a λ-type transition around TC. The second order nature of the transition has been confirmed by plotting universal curve with the isothermal magnetic entropy change vs temperature data. Electrical resistivity is metal-like in the paramagnetic region. Both electrical resistance and thermopower shows a slope change near TC. Temperature dependence of thermal conductivity of Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Al2 is as that of a metal.

The spin Hall magnetoresistance (SMR) of Pt/FeCoB bilayers with in-plane magnetocrystalline anisotropy was analysed with respect to a second order effect in the sensing current which acts, through the spin Hall effect in Pt, as a torque on the magnetization of the ferromagnetic layer and changes slightly its configuration. This leads to a small current dependent shift of the SMR curves in field that allows, in structures with a multidomain state (e.g. Hall bars), the determination of the sign of the magnetic remanence. The SMR measurements were performed as a function of the Pt thickness and the spin Hall angle, the diffusion length and the field-like and damping like SOT efficiency were determined. The results were compared with the values obtained from harmonic Hall voltage and SOT-ferromagnetic resonance (FMR) measurements and show a good agreement.

The electrodeposition technique was used to synthesize copper-doped ZrO2 thin film. Different characterization technique such as vibrating sample magnetometry, UV–visible spectroscopy, scanning electron microscope, and X-ray diffractometry were used to study the magnetic, optical, surface morphology, and structural properties of the thin films. The Uniform nanocrystalline grains without cracks, and of various sizes were obtained. The optical studies showed a decrease in energy band gap from 4.1 eV to 3.9 eV. The magnetic studies revealed that the doped samples have unique ferromagnetic ordering, this could be due to the increase in grain size. The 2% and 4% doped samples are saturated around 4.51 × 10−4 emu/g and 4.70 × 10−4 emu/g at coercive field of 274.54 and 274.96 respectively.

Nanostructured HoFeO3 powders were obtained by solution combustion method at various glycine-nitrate ratios (G/N = 0.2, 0.4, …, 1.4). According to X-ray powder diffractometry data, the presence of two modifications of HoFeO3 in the synthesized samples was established: orthorhombic (Pbnm) and hexagonal (P63/mmc). The crystallite size of the obtained compositions varies from 62 ± 6 to 29 ± 3 nm, depending on the G/N ratio. From magnetic structure studies, it is found that HoFeO3 obtained with a stoichiometric amount of glycine in the reaction solution is in the magnetically ordered state and is represented by a sextet with quadrupole splitting (QS) = 0 mm/s, isomeric shift (IS) = 0.36 mm/s and effective field strength (Heff) = 497 kOe. According to the results of vibrational magnetometry, it is found that the orthoferrites obtained have a ferromagnetic structure, the main parameters of which (Ms, Mr and Hc) systematically change with a change in the redox ratio of the reaction mixture and, as a consequence, their phase composition, and reach maximum values at a G/N ratio = 0.6. In the samples obtained with a significant excess and lack of glycine (G/N = 0.2 and 1.4), despite their amorphous nature, hysteresis loops characteristic of the ferromagnetic state of the substance is observed. It is hopeful to obtain a pure hexagonal modification of HoFeO3 via heat treatment on amorphous products of glycine-nitrate combustion.

In this study, we synthesized La1-xMgxFeO3 (x = 0.1, 0.2, and 0.3) powdered ceramics using sol − gel and sintering methods and their structure, magnetic and electrical properties have been investigated. All samples showed the Pbnm single phase, and structural analyses revealed a lattice distortion due to the addition of Mg that increases with increasing Mg content. Transmission electron microscopy revealed a decrease in particle size with increasing Mg content. The M − H hysteresis loops of the samples revealed that the samples with Mg substitution at the La site exhibits weak ferromagnetic behaviour, and the hysteresis loops increases with an increase in Mg content. The magnetisation increases as the Mg content is increased, which is might be related to the lower crystallite and particle sizes, as well as higher Fe4+/Fe3+ ratio, as shown by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. Analysis of the electrical properties showed grain–grain boundary effect in the conduction mechanism and two relaxation mechanisms for low Mg contents (x ≤ 0.2), whereas only the grain effect and one relaxation mechanism were observed at higher Mg contents (x = 0.3). The temperature dependence of direct current conductivity obeys the Arrhenius law. The activation energy for the conduction mechanism decreased with an increase in the Mg content. These results contribute the important knowledge in promising the candidate electrode material in electrochemical application.

Over the past four years, the magnetism of 2D magnets has been extensively studied by the full arsenal of probing techniques. 2D magnets can be incorporated to form heterostructures with clean and sharp interfaces, which gives rise to exotic phenomena as a result of the interfacial proximity effect. Here we report a detailed study of the spin (ms) and orbital (ml) moments of an epitaxial (CrSb/Fe3GeTe2)6 superlattice. The synchrotron-radiation based x-ray magnetic circular dichroism (XMCD) technique was performed to probe the microscopic magnetic properties of the superlattices in an elemental resolved manner. We unambiguously obtained a bulk-like moment of Fe3GeTe2 i.e., ms = 1.58 ± 0.2 μB/Fe and ml = 0.22 ± 0.02 μB/Fe. Future works to explore the tuning of the spin polarized band structure of 2D ferromagnetic superlattices will be of great interest and can have strong implications for both fundamental physics and the emerging spintronics technology.

The Fe and Co single and co-doping effects on the structural and magnetic properties of NiO nanoparticles (NPs) have been studied. The Fe and Co doping into NiO system did not induce any other possible secondary phase (other than NiO) and the average crystallite size was found to be in a narrow range of 33–40 nm which is suitable for studying the doping effects. Room temperature ferromagnetic resonance (FMR) measurements demonstrated the existence of a net magnetization in antiferromagnetic (AFM) NiO NPs which was observed to be increased with an increasing Fe doping and decreasing Co doping concentration. The scattered differential FMR signal for 8% Co doped NiO NPs revealed the presence of randomly oriented magnetic moments in the core of the NPs. However, decreasing the Co doping concentration and increasing the Fe doping concentration increased the degree of homogeneity of the spin structure in the system. The M − H loops taken at room temperature with S-like shape confirmed the presence of a weak ferromagnetism in the Fe doped samples in accordance with FMR analysis and attributed to the double exchange mechanism in these NPs. In ZFC/FC curves, a small peak at low temperatures, in the range of 9–18 K for all the samples, indicates the magnetization contribution from the uncompensated surface spins of these NPs. In addition, a relatively broad peak for higher Fe doping concentrations at higher temperatures indicates the onset of magnetization from the core of these NPs, where Fe and Ni ions may couple parallel or anti-parallel to each other. In summary, Co–Fe co-doping induced a core magnetization in AFM NiO NPs system and makes it attractive for various magnetic applications.

We report the critical behavior of the magnetization in Heusler alloy Co2TiGa0.8Sn0.2 as a potential candidate of high spin polarized materials with the characteristics of topological Weyl fermions. The Weyl semimetals are materials of great interest for applying spintronics devices, due to their unusual magnetoelectronic and magnetothermal properties. The magnetic properties of the synthesized Heusler alloy Co2TiGa0.8Sn0.2 are investigated around the Curie temperature TC. The magnetic isotherm measurements of Co2TiGa0.8Sn0.2 around TC exhibit that the critical exponent δ is deduced to be 4.455(4) in high maximum applied field of 50 kOe and 4.823(9) in low maximum applied field of 10 kOe, respectively. Both δ values are different from 3.0 derived by the conventional molecular field theory, but they are close to 5.0 predicted by the spin fluctuation theory for the itinerant electron ferromagnets. Possible origins for the discrepancy between experimental results and theoretical models are also discussed.

The synthesis of Ce doped ZnO nanoparticles exhibits the enhancement of results and its favor to electronic properties. The minimum average crystal size was obtained from 8 wt% (8 nm). The weight percentage (wt%) of cerium doping concentration increases, average crystal sizes are decreased upto 8 wt% and then crystal size increased for 10 wt% of doping level. The UV–Visible spectra analysis shows that the high absorbance and broad peak obtained at 8 wt%. PL studies exhibits the enhanced intensity of the broad emission at green region confirms that the increased density of defects which can be attributed to the oxygen vacancy created by the existence of Ce doped in ZnO nanoparticles. At last we got minimum band gap energy value of 1.32 eV at 8 wt% of Ce doped ZnO nanoparticles. VSM studies showed room temperature ferromagnetism in the Ce-doped ZnO NPs. The polarization esteems are seen as diminished with the expansion in Ce fixation in ZnO after 4 wt% and 6 wt% Ce. The watched ferromagnetism in Ce–ZnO NPs is because of the nearness of Ce3+ particle state and oxygen opening and interstitial destinations of Zn.