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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.

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.

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.

A promising magnetocaloric effect has been obtained in Ni-(Co)-Mn-X (X = Sn, In, Sb)-based Heusler alloys, but the low isothermal magnetic entropy change ΔSM restricts the further promotion of such materials. Defect engineering is a useful method to modulate magnetic performance and shows great potential in improving the magnetocaloric effect. In this work, dense Ni vacancies are introduced in Ni41Mn43Co6Sn10 alloys by employing high-energy electron irradiation to adjust the magnetic properties. These vacancies bring about intense lattice distortion to change the distance between adjacent magnetic atoms, leading to a significant enhancement of the average magnetic moment. As a result, the saturation magnetization of ferromagnetic austenite is accordingly improved to generate a high isothermal magnetic entropy change ΔSM of 20.0 J/(kg K) at a very low magnetic field of ∼2 T.

In this paper, we investigate the structural, elastic, electronic, magnetic, and thermodynamic properties of BaNYO (Y = Mg, Ca, and Sr) quaternary Heusler alloy, using the full-potential linearized augmented plane wave (FP-LAPW) method. The generalized gradient approximation functional of Wu and Cohen (GGA-PBE) is used to calculate ground-state structural parameters; the electronic band structures have been improved with Tran–Blaha modified Becker–Johnson (TB-mBJ) parameterization scheme. Our results demonstrate that in the ferromagnetic phase, all the alloys BaNYO (Y = Mg, Ca, and Sr) are stable in type-2 configuration and are half-metallic ferromagnets (HMF) with gaps of 1.34 eV, 1.32 eV, and 1.29 eV, respectively, using the mBJ-GGA-PBE approximation. The obtained negative formation energy shows that BaNYO alloys have strong structural stability. The elastic constants were also calculated to comprehend their potential for valuable applications. The calculated total magnetic moment MT for all three alloys is consistent with the Slater–Pauling rule. The half-metallicity is maintained over a wide range of lattice constants making these alloys promising for spintronic and magnetoelectronic applications. Through the quasi-harmonic Debye model, in which the phononic effect is considered the effect of pressure P (0 to 20) and temperature T (0 to 1000) on the lattice constant, bulk modulus B, heat capacity, entropy S, and Debye temperature θD are investigated.

In this study, we investigated the electronic and magnetic properties of pure and Cr-doped $$Li_{2}O$$ semiconductor within the framework of density functional theory (DFT) with the Korringa-Kohn-Rostoker method combined with the coherent potential approximation (KKR-CPA). The pure $$Li_{2}O$$ compound proved to be an intrinsic semiconductor with an indirect band gap of 4.74 eV. However, Cr-doped $$Li_{2}O$$ ( $$Li_{2}O_{1-x}Cr_{x})$$ showed the characteristics of a metal with a spin polarization at the Fermi level less than 100%. $$Li_{2}O_{1-x}Cr_{x}$$ exhibits a ferromagnetic stable phase originating from strong hybridization existing between the d-orbitals of Cr and that of Oxygen and total magnetic moments ranging from −0.383 $$\mu _{B}$$ to −0.912 $$\mu _{B}$$ for a concentration in the interval between 10% and 25%, respectively. The formation energy was also been calculated to study the stability of the pure and doped compound. Finally, the value of the Curie temperature, which reaches 780 (K), exceeds the ambient temperature, revealing the potential use of this doped material for new spintronic devices.

The spintronic properties of molecules are essential for the development of multifunctional organic spintronic devices. Here, the spin polarization of bis-(8-hydroxyquinoline) zinc (Znq2) molecule upon electron and hole injection has been theoretically studied by using density-functional theory calculations. It is found that both the injected excess electrons and holes are highly spin polarized in Znq2, leading to an approximately linearly increased magnetic moments with the amount of the charge injected. Our calculation also reveals that the spin polarization upon excess electron and hole injection may attribute to the exchange splitting of lowest unoccupied molecular orbital (LUMO)-related p states of N and C atoms of pyridyl rings and the highest occupied molecular orbital (HOMO)-related p states of O and C atoms of the phenoxide rings, respectively. The d0 ferromagnetism in the charge-injected Znq2 molecule is quite promising for organic spintronic devices.

Understanding the interplay between strain and nonstoichiometry for the electronic, magnetic, and redox properties of LiMn2O4 films is essential for their development as Li-ion battery (LIB) cathodes, photoelectrodes, and systems for sustainable spintronics applications as well as for emerging applications that combine these technologies. Here, density functional theory (DFT) simulations suggest that compressive strain increases the reduction drive of (111) LiMn2O4 films by inducing >1 eV upshift of the valence band edge. The DFT results indicate that, regardless of the crystallographic orientation for the LiMn2O4 film, biaxial expansion increases the magnetic moments of the Mn atoms. Conversely, biaxial compression reduces them. For ferromagnetic films, these changes can be substantial and as large as over 4 Bohr magnetons per unit cell over the simulated range of strain (from -6 to +3%). The DFT simulations also uncover a compensation mechanism whereby strain induces opposite changes in the magnetic moment of the Mn and O atoms, leading to an overall constant magnetic moment for the ferromagnetic films. The calculated strain-induced changes in atomic magnetic moments reflect modifications in the local electronic hybridization of both the Mn and O atoms, which in turn suggests strain-tunable, local chemical, and electrochemical reactivity. Several energy-favored (110) and (111) ferromagnetic surfaces turn out to be half-metallic with minority-spin band gaps as large as 3.2 eV and compatible with spin-dependent electron-transport and possible spin-dependent electrochemical and electrocatalytic properties. The resilience of the ferromagnetic, half-metallic states to surface nonstoichiometry and compositional changes invites exploration of the potential of LiMn2O4 thin films for sustainable spintronic applications beyond state-of-the-art, rare-earth metal-based, ferromagnetic half-metallic oxides.

The transverse Rashba effect in a centrosymmetric antiferromagnet materialized by double-Gd-adsorbed graphene nanoribbon is investigated via the first-principle calculations. The Rashba effect is associated with not only the local transverse dipole fields induced by the off-center adsorption of the Gd adatoms but also the local magnetic moments. It is perfectly realized that the transverse Rashba effect (Rashba parameter αx reaches to 2.205 eV A) and strong perpendicular magnetocrystalline anisotropy energy (MAE) coexist in antiferromagnetic (AFM) ground-state structure. However, the global Rashba effect disappears in ferromagnetic structure. The origin of the strong MAE is elaborated in k − space. It is intriguing that the first-order perturbation of the orbit and spin angular momentum coupling is the major source of the MAE due to the specific one-dimensional band structure. The transverse Rashba effect and the strong perpendicular magnetization hosted simultaneously by the proposed centrosymmetric antiferromagnet lock the up- (or down-) spin quantization direction (SQD) to the backward (or forward) movement, and the SQD is related to the chirality of the AFM structure. This finding offers a magnetic approach to a high coherency spin propagation in one-dimensionality, and open a new door to manipulating spin transportation in graphene nanoribbon-based spintronics.

In light of existing literature of stable ferromagnetic phase, the thermoelectric and optical behavior of the Cd-based spinel chalcogenides i.e. CdCr2X4, (X = S, Se, Te) were inspected and their structural and electronic characteristics were examined in terms of density functional theory calculations. The negative values of formation energy of said spinels were calculated to confirm their ferromagnetic phase stability. Optimization of band structure and calculations of density of states confirmed their ferromagnetic nature. For both channel, the band structure exhibited the semiconducting behavior. The exchange constants (N0α and N0β) were investigated with the help of exchange splitting energies, which were explored from the density of states. The splitting of 3d-states of Cr were explained on the basis of larger value of N0β as compared with N0α. Owing to the strong p-d hybridization indicated by N0β = −0.11, −0.12 and −0.15 and N0α = 0.14, 0.32 and 0.44 for CdCr2S4, CdCr2Se4 and CdCr2Te4, respectively, the necessary condition for ferromagnetic system is satisfied showing that exchange field dominates over the crystal field that induces the ferromagnetism in these spinels. Moreover the p-d hybridization was used to decrease the magnetic moment at Cr ions, by using a fraction of magnetic moment at non-magnetic sites. Further, optical characteristics were investigated in terms of photon energy 0–6 eV showing less dispersion of light and refractive index ranges up to 1–1.5 in visible region, thus suggesting spinels as potential candidates for opto-electronic applications. The thermoelectric performance observed in the temperature range of 200–600K which indicate positive Seebeck coefficients of ∼250 CdCr2S4, CdCr2Se4 while a negative Seebeck coefficients of −112 for CdCr2Te4 at room temperature. Further the power factors increased from S to Te as well as with increase of temperature which shows the potential of these chalcogens for thermoelectric power generators.

All-optical switching of magnetization has great potential for use in future ultrafast and energy efficient nanoscale magnetic storage devices. So far, research has been almost exclusively focused on rare-earth based materials, which limits device tunability and scalability. Here, we show that a perpendicularly magnetized synthetic ferrimagnet composed of two distinct transition metal ferromagnetic layers, Ni3Pt and Co, can exhibit helicity independent magnetization switching. Switching occurs between two equivalent remanent states with antiparallel alignment of the Ni3Pt and Co magnetic moments and is observable over a broad temperature range. Time-resolved measurements indicate that the switching is driven by a spin-polarized current passing through the subnanometer Ir interlayer. The magnetic properties of this model system may be tuned continuously via subnanoscale changes in the constituent layer thicknesses as well as growth conditions, allowing the underlying mechanisms to be elucidated and paving the way to a new class of data storage devices.

First-principles calculations accomplished to investigate structural, mechanical, thermal and magnetic properties of newly designed CoNbCrZ (Z = Al, Ga, Si, Ge) Heusler alloys (HAs). Generalized gradient approximation (GGA) and Hubbard potential (GGA + U) are used as exchange correlation functional. Geometry optimization calculations show that all these HAs are stable in Type I structure. Further calculations are carried out for non-magnetic (NM) and magnetic phases and found that all considered alloys are stable in ferromagnetic (FM) phase. GGA and GGA + U approximations executed to obtain electronic structures of CoNbCrZ (Z = Al, Ga) HAs, while GGA approximations performed for CoNbCrZ (Z = Si, Ge) HAs. Magnetic properties revealed that following alloys i.e. CoNbCrAl and CoNbCrGa are complete half-metals (HM) while CoNbCrSi and CoNbCrGe are NM semi-metals in nature. All these alloys are obeying Slater-Pauling rule (Mt = 24-Zt) and calculated magnetic moments are in well agreement. Mechanical parameters show that all alloys are stable and ductile in nature as well as have anisotropic behavior. High Debye temperature and melting temperature also authenticate the thermal stability of these alloys. Furthermore, negative formation (Ef) energy indicated that all these alloys could be synthesized experimentally.

According to the first principles, the WIEN2k program based on density functional theory (DFT) calculations is utilized to investigate the structural, magnetic, electronic, and optical properties of rare-earth vanadate perovskites PrVO3 (PVO) and NdVO3 (NVO). All calculations were performed by utilizing the full-potential linearized augmented plane wave (FP-LAPW) method within the generalized gradient approximation (GGA) under the potentials PBE-GGA, PBEsol-GGA, and WC-GGA. The optimized results show that the two compounds PVO, and NVO crystallize in a cubic structure with (Pm-3m) space group (No. 221) and lattice constants of (a = 3.8100 –3.8900 A). Partial and total spin magnetic moments confirm the ferromagnetic (FM) nature of these compounds, and the major part of their total magnetic moments (MCell ≈ 4.0 and ≈ 5.0 μB) is contributed by V3+ ions through the FM 3d-2p exchange interaction V3+↑–O2−↓–V4+↑ within the ground-state energies. The calculated spin-polarized electronic band structures, density of states, and charge density indicate that PVO and NVO exhibit a half-metallic property for all three GGA potentials. It is found that PBE-GGA gives reasonable results consistent with the previous data. Also, the main optical features are calculated and discussed to complete the description of the distinctive physical properties of these materials.

In this work, α-phase Fe-12 V alloy (at.%) with high total magnetostriction is selected to perform Mossbauer and Vibrating Sample Magnetometer (VSM) measurements to investigate the temperature dependence of atomic clusters and the magnetic properties. The results show that with increasing temperature, the ferromagnetism firstly drops and then slightly increases, and finally decreases severely, which is mainly determined by the variations of the three kinds of atomic clusters (Fe-rich, V-rich and free-Fe) in the alloy. The hyperfine magnetic field, which decreases with temperature, is always dominated by the Fe-rich clusters. The atomic combination of the free-Fe clusters also determines the magnetic properties in the temperature range from room temperature to 600 °C; however, the free-Fe clusters contribution to the hyperfine magnetic fields tends to become zero above 600 °C, whereas that of the V-rich becomes obvious. When the temperature is high enough, the hyperfine magnetic field decreases sharply due to the destruction of the ordered Fe-rich state. VSM was selected to understand the relationship between the magnetic moment and the heating temperature, and the Curie temperature (TC=836.36 °C) of the Fe-12 V alloy was obtained as well. Finally, the formula reflecting the magnetic moment of the α-phase Fe-12 V alloy varying with temperature is also successfully derived.

We report the results of micromagnetic simulations of low-frequency resonances associated with gyrotropic motion of exchange-coupled magnetic vortices in a system of two overlapping ferromagnetic disks. The dependences of the resonance frequencies on the method of excitation, the mutual direction of the vortex cores and on the external magnetizing magnetic field are analyzed. The modeling demonstrates that the most effective influence on the change in the resonance frequency is realized when the system is magnetized in the sample plane in the direction perpendicular to the line connecting the disks centers, opposite to the direction of magnetization in the area of disks overlapping. It is shown that for the state with opposite core polarity there are two resonant modes in which the cores and consequently the in-plane dipole moments induced in vortex shells are rotated in the opposite directions. On the contrary, in the resonant mode of the state with the same core polarity, the cores are rotated in the same directions and induced dipole moments are rotated in phase. The possibilities of using the overlapping disks system for the synchronization of vortex nano-oscillators are discussed.

We perform magnetic susceptibility and magnetic torque measurements on the organic $\kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$Br, which is recently suggested to host an exotic quantum dipole-liquid in its low-temperature insulating phase. Below the metal-insulator transition temperature, the magnetic susceptibility follows a Curie-Weiss law with a positive Curie-Weiss temperature, and a particular $M\propto \sqrt{H}$ curve is observed. The emergent ferromagnetically interacting spins amount to about 1/6 of the full spin moment of localized charges. Taking account of the possible inhomogeneous quasi-charge-order that forms a dipole-liquid, we construct a model of antiferromagnetically interacting spin chains in two adjacent charge-ordered domains, which are coupled via fluctuating charges on a Mott-dimer at the boundary. We find that the charge fluctuations can draw a weak ferromagnetic moment out of the spin singlet domains., Comment: 9 pages, 5 figures, Supplementary Material attached

In this paper, we present the results obtained from our study on the heat current across double quantum dots in serial coupled to ferromagnetic leads (FM-DQDs-FM), when the leads magnetic moments are in antiparallel configuration. This study was done by using nonequilibrium Green's function method in the linear response regime. Our results are calculated in weak interdot coupling regime by taking all the parameters that affect the system such as intradot Coulomb correlation energy, spin–spin exchange interaction, and spin polarization on the leads. These results are accomplished as a function of temperature gradient as well as quantum dots energy levels. According to our results, it is noticed that the values of intradot Coulomb correlation energy and the spin–spin exchange interaction have significant impact on increasing the heat current that flows through our system. It is concluded that increasing or decreasing the magnitude of heat current in negative or positive thermal bias is ideal for designing high-efficiency heat diode.

Double perovskite oxides have attracted much attention in material science and spintronic applications due to their exceptional physical properties. In this paper, the transition-metal double perovskite oxides Sr2MNbO6(M = V, Cr) are studied to investigate the effect of the magnetic cation M, using the full-potential linearized augmented plane wave method (FP-LAPW) within a generalized gradient approximation (GGA), Hubbard correction (GGA + U), and exact exchange for correlated electrons (EECE) in the framework of the density functional theory (DFT). The cubic phase is the most stable polymorph in the ambient condition for both double perovskites. The lattice parameters, interne coordinates, are in agreement with previous measurements and theoretical calculations. Furthermore, both of the examined materials are brittle in nature and have an elastically anisotropic character. More importantly, for Sr2VNbO6, a half-metallic ferromagnetism is predicted with a narrow band gap in the minority spin, whereas Sr2CrNbO6 shows a ferromagnetic insulator nature, and the estimated Curie temperatures are higher than the room temperature. We deduce that the M3+ (3dn- $${\mathrm{t}}_{2g}^{n};S=\frac{n}{2}$$ ) ions (n = 2or 3) have a significant effect on the magnetic moment and the electronic conducting, on the contrary to the nonmagnetic Nb5+ (4 d0- $${\mathrm{t}}_{2g}^{0}$$ ) ions. The thermodynamic properties are predicted in the temperature range from 0.0 to 1000 K where the quasi-harmonic model remains fully valid. These results indicate that Sr2MNbO6 might have an important potential application in spintronic devices.

The object of this study is to investigate the half-metallicity, electronic structures and magnetic in the Ba1 – xMnxO compounds under the effect of substitution of Mn impurity at the different composition x = 0.25, 0.5, and 0.75 by the use of density functional theory (DFT) based first principle calculations. The half-metallic ferromagnetism is explained by analyzing the density of states. The ferromagnetic states configuration is originated from the 3d-eg (Mn) partially filled states associated with p–d exchange mechanism. For the three concentrations, the total magnetic moment is integral member, which is mainly contributed by the magnetic moment Mn atom. We have found that Ba0.75Mn0.25O, Ba0.5Mn0. 5O and Ba0.25Mn0.75O compounds have direct half-metallic ferromagnetic gaps of 0.834, 0.58 and 0.368 eV, respectively, which decrease with increasing Mn concentration. Therefore, the Ba1 – xMnxO materials seem to be potential candidates for possible applications of semiconductor spintronics.

In this study, the electronic structures and magnetic and elastic properties of Cr2FeZ (Z = Sb, As) Heusler alloys were investigated through density functional theory calculations, which uses the generalized gradient approximation for the exchange-correlation functional included in the CASTEP software package. The results revealed that the Cr2FeSb and Cr2FeAs alloys successfully formed stable Hg2CuTi-type structures at finite temperatures. The ground-state properties of the stable structures were calculated, including lattice parameters, magnetic moments, and bulk moduli. The Cr2FeSb and Cr2FeAs alloys exhibited nearly half-metallic properties and high spin-polarization levels and thus can be used as half-metal/ferromagnetic metal (HM-FM) materials.

The search for functional materials in spintronic devices has become a major component of material research in recent times. The structural, elastic, mechanical, electronic and magnetic properties of half-Heusler FeCrAs alloy (HHFCA) have been examined adopting spin-polarized density functional theory calculations. Our result shows that the hexagonal structure is the high pressure phase of the FeCrAs alloy while the half-Heusler structure is the more stable phase at ambient pressure. Also, the HHFCA is mechanically stable and exhibits half-metallic ferromagnetism besides an indirect band gap in the minority spin channel. The total magnetic moment in one formula unit of the alloy is 1.00 μB, in agreement with the Slater-Pauling rule and the bulk of the magnetic moment contributed by the Cr atoms. Furthermore, high Curie temperature of ~ 1000 K has been obtained for the HHFCA which suggests that it is a promising material for spintronic applications.

Integrating characteristics of materials through constructing artificial superlattices (SLs) has raised extensive attention in multifunctional materials. Here, we report the synthesis of BiFeO3/BiMnO3 SLs with considerable ferroelectric polarizations and tunable magnetic moments. The polarization of BiFeO3/BiMnO3 SLs presents a decent value of 12 μC/cm2, even as the dimensionality of BiFeO3 layers per period is reduced to about five-unit cells when keeping the BiMnO3 layers same. Moreover, it is found that the tunable magnetic moments of SLs are linked intimately to the dimensionality of BiFeO3 layers. Our simulations demonstrate that the superexchange interaction of Fe-O-Mn tends to be antiferromagnetic (AFM) with a lower magnetic domain formation energy rather than ferromagnetic (FM). Therefore, as the dimensionality of BiFeO3 per period is reduced, the AFM superexchange interaction between BiFeO3 and BiMnO3 in the SLs becomes weak, promoting a robust magnetization. This interlayer modulation effect in SLs presents an alluring way to accurately control the multiple order parameters in a multiferroic oxide system.

The electronic, optical, and transport properties of new d0 half-Heusler alloys SiLiX (X = Ca, Sr) were studied by using the first-principles method and semi-classical Boltzmann theory. The results of the electronic properties reveal for both half-Heusler the half-metallic ferromagnetic nature (HMF) with a direct gap of 1.401 eV and large half-metallic gap of 0.42 eV for SiLiSr alloy, while the SiLiCa compound shows an indirect band gap of 1.209 eV and half-metallic gap of 0.21 eV. The same magnetic moment of 1.00 μB per formula was observed for the two alloys. The optical computations indicate that SiLiX half-Heusler is active in a wide area of the electromagnetic spectrum. The high reflectivity of SiLiX alloys, which is well above 43% in the ultraviolet region and 38% in the near infrared region, let us use them as an effective shield in these domains. Around 300 K, the thermal conductivity was reduced by approximately 54%, following the replacement of calcium by strontium in the X site. The zT values very close to unity were reported in large temperature range. The obtained results reveal that the studied materials could be used efficiently for the applications of optical and thermoelectric devices.

Magnetic semiconductors with high Curie temper (TC) and inherent ferromagnetism, which not only provide a data-processing function via semiconductors' properties, but also offer a data-storage function through intrinsic ferromagnetism, have become key materials in the field of spintronics. We studied the electronic structures and magnetic properties of Mn-doped cubic (3C) SiC using first-principles calculation. The calculated results revealed that MnSi and MnC substitutions can introduce 3 $$\mu _{{\text{B}}}$$ and 1 $$\mu _{{\text{B}}}$$ magnetic moments into SiC, respectively, which are both localized and extended. The extended tails of the moments indicate a significant spatial extension of the spin-polarized electron states. The interaction between the long tails, which can mediate long-range ferromagnetic (FM) coupling up to 8.55 A, and is very different from common exchange, in which the ferromagnetism decreases sharply with increasing distance between the moments, and is hard to maintain to the next-neighbor order due to the limited spatial spin-electrons distribution. The distributions of magnetic moments become more and more localized or extended as compressive or tensile strains are increased, but FM interactions under compressive and tensile strains are weaker than those in undeformed structure. The FM coupling mechanism is explained and discussed in detail using p–d electron exchange. These results can provide a routine for engineering FM semiconductor of 3C-SiC.

The matrix method of Tsai for the calculation of the nonlocal exchange potential has been extended to calculate the plain-wave expanded interstitial part using the Thomas-Fermi damping wave vector. We found enhancement of the 3 d -band exchange splitting and consequently the magnetizations and magnetic moments relative to those obtained by LSDA. By resolving the valence electrons of the Fe, Co, and Ni atoms into spin-polarized s, p, and d components, we found depletion of the itinerant 4 s p electrons that enhances the minority-spin localized d electrons, which is the main cause of the substantial reduction of the magnetic moments in the metals from those of free atoms. Using idealistic domain-wall-free structural models, the magnetizations of these three metals calculated by the exchange-matrix method are overestimated. The overestimates correlate with the exchange energies, which may play a determinative role in the sizes of domain walls.

The effects of site occupation on the phase stability, martensitic transformation, and the magnetic and electronic properties of a full series of Ni-Mn-In alloys are theoretically studied by using the ab initio calculations. Results indicate that the excess atoms of the rich component directly take the sublattices of the deficient components of the Ni2Mn1+xIn1-x, Ni2-xMn1+xIn, and Ni2+xMn1-xIn alloys. Nevertheless, the mixed and indirect site occupations may coexist in the Ni2+xMnIn1-x system. The relevant magnetic configurations of the austenite for the four alloy systems have also been determined. The results show that, except for the austenite in the Ni2-xMn1+xIn alloys, which tend to be ferrimagnetic, the other alloys all present ferromagnetic austenite. Thus, the site occupation and associated magnetic states are the crucial influencing factors of the phase stability, martensitic transformation, and the total magnetic moment. The electronic structure of the austenite phase also shows that the covalent bonding plays an important role in the phase stability. The key finding of this work is both Ni2Mn1+xIn1-x and Ni2+xMnIn1-x alloys serve as the potential shape memory alloys.

Heavy Fermion (HF) states emerge in correlated quantum materials due to the intriguing interplay between localized magnetic moments and itinerant electrons but rarely appear in 3d-electron systems due to high itinerancy of d-electrons. Here, an anomalous enhancement of Kondo screening is observed at the Kondo hole of local Fe vacancies in Fe3GeTe2 which is a recently discovered 3d-HF system featuring Kondo lattice and two-dimensional itinerant ferromagnetism. An itinerant Kondo-Ising model is established to reproduce the experimental results and provides insight into the competition between Ising ferromagnetism and Kondo screening. Our work explains the microscopic origin of the d-electron HF states in Fe3GeTe2 and inspires future studies of the enriched quantum many-body effects with Kondo holes.

The electronic structure and magnetism of Mn2SnS4 are analysed with full-potential first-principles calculations. In order to understand the possible influence of magnetic structure, we have performed calculations of total energies for both ferromagnetic (FM) and antiferromagnetic (AFM) orderings. Antiferromagnetic ordering is of three types. Our computed results reveal that Mn2SnS4 exhibits an AFM-I type antiferromagnetic ordering. The exchange interaction parameters, which reflects the electrostatic Coulomb repulsion of electrons on neighboring atoms and the Pauli principle, were estimated to be J1 = − 14.1 meV, J2= − 5.3 meV and J3 = − 8.2 meV according to the Heisenberg model. It was shown that all values are negative and J1 has the highest absolute value, demonstrating strong antiferromagnetic pairing dominating between the nearest magnetic Mn ions and weak antiferromagnetic coupling within the next-nearest Mn ions. The position of the sulfur atoms have no impact on the values of the aforementioned energies, which validates that the magnetism in Mn2SnS4 is dominated mainly by direct exchange. The associated energy differences involving spin orderings can be used to evaluate the critical temperature of the compounds Mn2SnS4. Our calculations show that taking into account the spin–orbit coupling has no significant effect on the accuracy of the band gap of Mn2SnS4. The calculated results of equilibrium volume, antiferromagnetic ordering type, local magnetic moment, and band gap are in good agreement with reported experimental results. The relative differences between spin configurations can be used to derive observables such as Curie-Weiss temperature (θ). The Curie-Weiss temperature is calculated using the mean-field approximation. Reasonable agreement with the experiment is found for all properties including the equilibrium volume, local magnetic moment, antiferromagnetic ordering type, band gap, and the Curie-Weiss temperature.

At present, the studies on magnetocaloric properties are mainly based on polycrystalline materials, which is not enough to reveal and understand the origin of their magnetocaloric effect. In addition, finding new room temperature magnetocaloric materials is crucial to the development and application for room temperature magnetic refrigeration. Here, we report the magnetic transitions, magnetic anisotropy, and magnetocaloric properties of single-crystal Mn5Ge3 and Mn5Ge3/Mn3.5Fe1.5Ge3 heterostructures with six (100) surfaces and the [001] growth direction prepared using the Sn flux method. Mn5Ge3 (Mn3.5Fe1.5Ge3) undergoes a sharp paramagnetic-collinear ferromagnetic transition at 299 (332) K and weak collinear-noncollinear ferromagnetic transition at 65 (35) K. Owing to the distinct spin arrangements and magnetic moments of Mn5Ge3 and Mn3.5Fe1.5Ge3, the magnetic anisotropy of the single crystal is stronger than that of the heterostructure below 299 K. Moreover, a large anisotropic magnetocaloric effect, wide operating temperature range, and large refrigeration capacity near room temperature are obtained in these two materials, especially the magnetocaloric effect of the heterostructure presents a tablelike shape due to the adjacent paramagnetic-collinear ferromagnetic transitions of Mn5Ge3 and Mn3.5Fe1.5Ge3. Under 0-3 T, the maximum magnetic entropy change, operating temperature range, and refrigeration capacity of the single crystal (heterostructure) are 5.19 (2.96) J kg-1 K-1, 43 (57) K, and 223 (169) J kg-1 when H//c, respectively. These features make them candidates for room temperature magnetic refrigeration.

Layered Fe/MgO/Cr/MgO/Fe nanostructures are an artificial ferromagnetic material, in which the exchange interaction of the magnetic moments of the Fe layers through intermediate dielectric and metal layers can lead to magnetic configurations that are not implemented in well-studied Fe/MgO/Fe and Fe/Cr/Fe systems. The correlation between the structural and magnetic properties of layered nanoheterostructures Fe(10 nm)/MgO(1.5 nm)/Cr(t)/MgO(1.5 nm)/Fe(7 nm) (t = 0.9, 1.8 nm) is studied. The data of X-ray diffractometry and high-resolution reflectometry confirm the formation of an epitaxial crystal structure and reveal its layered nature with sharp interlayer boundaries. Vibration magnetometry does not reveal substantial differences in the hysteresis loops, which have a characteristic stepped shape. Polarized neutron reflectometry makes it possible to establish that the processes of magnetization reversal in these samples occur in different ways at the level of individual Fe layers. In the sample with Cr interlayers with a thickness of 0.9 nm, the Fe layers are exchange coupled through the MgO/Cr/MgO interlayer, and their rotation is correlated upon applying a magnetic field. There is no exchange interaction between the Fe layers in the sample with a Cr interlayer with a thickness of 1.8 nm, and they undergo magnetization reversal independent of each other. It is found that the magnetization reversal of the Fe/MgO/Cr/MgO/Fe systems is characterized by an intermediate state that can be controlled using a small external field with an intensity of several tens of oersted and a change in the orientation of the sample as well as by varying the thickness of the MgO layer.

This work details the construction and optimization of a fully automated, custom-built, remote controlled vibrating sample magnetometer for use in spintronics related research and teaching. Following calibration by a standard 6 mm diameter Ni disc sample with known magnetic moment, hysteresis measurements of Nd-Fe-B thin films acquired by this built vibrating sample magnetometer were compared to the data taken using a commercial superconducting quantum interference device and showed very similar results. In plane and out of plane magnetic hysteresis data acquired for 25 nm Fe thin films are also presented. The developed vibrating sample magnetometer is able to achieve a sensitivity approaching 1 × 10−5 emu. Further alterations to the design that may improve beyond this limit are also discussed.

In this study, we use the Quantum Espresso code under the pseudo-potentials wave method based on density functional theory (DFT) to investigate the structural, electronic, and magnetic properties of the rare earth-based solar perovskites GdAlO3, DyAlO3, and HoAlO3 materials. In fact, the optimized unit cells for each one of these materials have been used to explore the stability and the ferromagnetic behavior of such materials. It is found that the cubic perovskite HoAlO3 material is the more stable structure, while the compound DyAlO3 is more stable than GdAlO3 alloy in this structure. On the other hand, the band structure and density of states confirm that the GdAlO3 perovskite has a semiconductor nature, while the DyAlO3 and HoAlO3 exhibit a half-metallic ferromagnetic character. In addition, the spin-polarized magnetic moments of these compounds reveal that these materials show a ferromagnetic nature. Moreover, the calculated magnetic moments of the cubic GdAlO3, DyAlO3, and HoAlO3 are 7.02 μB, 5.00 μB, and 4.00 μB, respectively. Furthermore, the obtained results approve that these compounds could be promising materials for spintronic and optoelectronic devices. Moreover, such materials are promising candidates for photovoltaic applications.

Recent discoveries of intrinsic two-dimensional (2D) magnets open up vast opportunities to address fundamental problems in condensed matter physics, giving rise to applications from ultra-compact spintronics to quantum computing. The ever-growing material landscape of 2D magnets lacks, however, carbon-based systems, prominent in other areas of 2D research. Magnetization measurements of the Eu/graphene compound—a monolayer of the EuC6 stoichiometry—reveal the emergence of 2D ferromagnetism but detailed studies of competing magnetic states are still missing. Here, we employ element-selective X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) to establish the magnetic structure of monolayer EuC6. The system exhibits the anomalous Hall effect, negative magnetoresistance, and magnetization consistent with a ferromagnetic state but the saturation magnetic moment (about 2.5 µB/Eu) is way too low for the half-filled f-shells of Eu2+ ions. Combined XAS/XMCD studies at the Eu L3 absorption edge probe the EuC6 magnetism in high fields and reveal the nature of the missing magnetic moments. The results are set against XMCD studies in Eu/silicene and Eu/germanene to establish monolayer EuC6 as a prominent member of the family of Eu-based 2D magnets combining the celebrated graphene properties with a strong magnetism of europium.

Titanium disulfide TiS$_2$, which is a member of the layered transition-metal dichalcogenides with the 1T-CdI$_2$-type crystal structure, is known to exhibit a wide variety of magnetism through intercalating various kinds of transition-metal atoms of different concentrations. Among them, Fe-intercalated titanium disulfide Fe$_x$TiS$_2$ is known to be ferromagnetic with strong perpendicular magnetic anisotropy (PMA) and large coercive fields ($H_\text{c}$). In order to study the microscopic origin of the magnetism of this compound, we have performed X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements on single crystals of heavily intercalated Fe$_x$TiS$_2$ ($x\sim0.5$). The grown single crystals showed a strong PMA with a large $H_\text{c}$ of $\mu_0H_\text{c} \simeq 1.0\ \text{T}$. XAS and XMCD spectra showed that Fe is fully in the valence states of 2+ and that Ti is in an itinerant electronic state, indicating electron transfer from the intercalated Fe atoms to the host TiS$_2$ bands. The Fe$^{2+}$ ions were shown to have a large orbital magnetic moment of $\simeq 0.59\ \mu_\text{B}\text{/Fe}$, to which, combined with the spin-orbit interaction and the trigonal crystal field, we attribute the strong magnetic anisotropy of Fe$_x$TiS$_2$., Comment: 24 pages, 8 figures

Non-stationary spin-dependent transport through the interacting single-level quantum dot coupled to ferromagnetic leads with non-collinear magnetizations has been analyzed theoretically. The non-stationary transport is investigated within the theoretical approach based on kinetic equations for the electron occupation numbers with different spins taking into account high order correlation functions for the localized electrons. It has been demonstrated that spin polarization, direction and amplitude of the non-stationary currents could be effectively changed in a rather simple system by varying the relative directions of the magnetic moments in the leads. The degree of the currents spin polarization also changes following the direction of magnetic moments in the leads. The results open a possibility for spin polarization control in nanoscale systems and are very promising in the sense of spin filtering.

We perform a first-principles calculation to understand the effect of the additional valence electron of the transition atom in Wyckoff position 4 a, on the electronic structure, magnetic and structural stability of the full Heusler $${\mathrm{Mn}}_{2}\mathrm{PtZ}(\mathrm{Z}=\mathrm{V and Co})$$ compound. L21, Xa and tetragonal structures are considered to verify the most stable phase. Within the framework of the plan $${\mathrm{Mn}}_{2}\mathrm{PtZ}(\mathrm{Z}=\mathrm{V and Co})$$ favored the ferromagnetic configuration in the L21 structure. The results show that the 63% and 91% spin polarization at the Fermi level for $${\mathrm{Mn}}_{2}\mathrm{PtV}$$ and $${\mathrm{Mn}}_{2}\mathrm{PtCo}$$ , respectively. The most contribution of the magnetic moment is due to the Mn atom, the total magnetic moments equal to $${4.87\upmu }_{\mathrm{B}}$$ and $${9.012\upmu }_{\mathrm{B}}$$ have been reported. To prove the half metallicity of our compound, we used the GGA + U approach. Within the framework of this approach, the value gap in the minority spin band is 0.755 eV, more, the magnetic moment satisfying the Slater-Pauling rule for the $${\mathrm{Mn}}_{2}\mathrm{PtV}$$ compound. In addition, we give the two values of the curie temperatures for the two cubic structural phases. Finally, both full Heusler $${\mathrm{Mn}}_{2}\mathrm{PtV}$$ and $${\mathrm{Mn}}_{2}\mathrm{PtCo}$$ are a promising candidate for the use of future devices as spin-FETs and nonvolatile magnetic memory.

This study investigates the structural stability, electronic, elastic, magnetic, thermodynamic, and thermoelectric properties of Ru2MnNb alloy by employing first-principles calculations based on the density functional theory (DFT). Using the generalized gradient approximation (GGA), it is found that the Ru2MnNb alloy is stable in the ferromagnetic (FM) state of Cu2MnAl type structure. The electronic results indicate that Ru2MnNb is a metal and has a conductive character; its magnetic moment is found to be 4.13 (μB). It is also found to be elastically stable and ductile. The thermodynamic properties of Ru2MnNb, such as volume variation (V), compressibility modulus (B), Debye temperature, thermal expansion (흰), specific capacity (Cp), and thermal capacity (Cv), are obtained by quasi-harmonic Debye model. At the end, the dependence of Seebeck coefficient (S), power factor, and figure of merit (ZT) on the Fermi level are investigated.

Light-matter strong coupling in the vacuum limit has been shown to enhance material properties over the past decade. Oxide nanoparticles are known to exhibit weak ferromagnetism due to vacancies in the lattice. Here we report the 700-fold enhancement of the ferromagnetism of YBa$_2$Cu$_3$O$_{7-x}$ nanoparticles under cooperative strong coupling at room temperature. The magnetic moment reaches 0.90 $\mu_{\rm B}$/mol, and with such a high value, it competes with YBa$_2$Cu$_3$O$_{7-x}$ superconductivity at low temperature. This strong ferromagnetism at room temperature suggest that strong coupling is a new tool for the development of next generations of magnetic and spintronic nanodevices., Comment: 24 pages, 4 figures - difference with v1 version: revised Supplementary Information file