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Magnetic semiconductors, with integrated properties of ferromagnets and semiconductors, are significant for developing next‐generation spintronic devices. Herein two atomically precise clusters of dysprosium(III) tellurides, formulated respectively as [Na2(15‐crown‐5)3(py)2][(η5‐Cp*Dy)5(Te)6](py)4 (Dy5Te6, Cp*=pentamethylcyclopentadienyl; py=pyridine) and [K(2,2,2‐cryptand)]2[(η5‐Cp*Dy)6(Te3)(Te2)2(Te)3] (Dy6Te10), are reported. Crystallographic studies revealed the presence of multifarious tellurido ligands within the polyhedral cluster cores. Spectroscopic and magnetic studies showed that both clusters are single‐molecule magnets exhibiting slow magnetic relaxation behaviors at low temperatures and semiconductors with low optical band gaps comparable to benchmark semiconductors. These clusters represent probably the first lanthanide‐based molecular magnetic semiconductors. [ABSTRACT FROM AUTHOR]

Abstract Geometrically perfect S = ½ kagome lattices with frustrated magnetism are typically electrical insulators. Electron or hole doping is predicted to induce an exotic conducting state including superconductivity. Herein, an unconventional strategy of doping an S = ½ kagome lattice CoCu3(OH)6Cl2 is adopted – a structural analogue of a well‐known quantum spin liquid (QSL) candidate herbertsmithite (ZnCu3(OH)6Cl2) – by integrating it with reduced graphene oxide (rGO) via in situ redox chemistry. Such an integration drastically enhances the electrical conductivity, resulting in the transformation of an insulator to a semiconductor, corroborating the respective density of states obtained from the density functional theory calculations. Estimation of the magnetic moments, data on the Hall‐effect measurements, Bader charge analysis, and photoemission signals, altogether provide a bold signature of remote hole doping in CoCu3(OH)6Cl2 by rGO. The remote doping provides an alternative to the site doping approach to impart exotic electronic properties in spin liquid candidates, specifically, the generation of topological states like Dirac metal is envisioned.

Layer‐ and stacking‐dependent interlayer magnetism observed in bilayer CrI3${\rm CrI}_3$ has attracted a lot of attention recently. Although considerable efforts have been made, the interlayer exchange mechanism still lacks a clear physical picture. In this paper, orbital overlap‐dependent super‐super‐exchange (SSE) interactions are proposed to understand the interlayer magnetism of bilayer MX3${\rm MX}_3$ (M = Cr, Fe, and Mo; X = Cl, Br, and I) with different stacking orders. The detailed atom‐ and orbital‐resolved magnetic exchange couplings are evaluated to reveal the underlying mechanism. The results suggest that the interlayer magnetic ground state of all FeX3${\rm FeX}_3$ bilayers are antiferromagnetism (AFM) due to the t2g3eg2$t_{2g}^{3}e_{g}^{2}$ electronic configuration of Fe3+${\rm Fe}^{3+}$ cation. While CrX3${\rm CrX}_3$ and MoX3${\rm MoX}_3$ are found to possess stacking‐dependent interlayer magnetism due to the competition between AFM and ferromagnetism (FM), the dominant interlayer AFM exchange couplings are the eg−eg$e_{g}-e_{g}$ and t2g−t2g$t_{2g}-t_{2g}$ for CrX3${\rm CrX}_3$ and MoX3${\rm MoX}_3$, respectively, indicating different underlying mechanisms. These distinct interlayer magnetism can be consistently understood by the number and strength of SSE paths, which can be determined by the rule based on the orbital overlap of mediating anions. Moreover, the atom‐ and orbital‐resolved magnetic exchange couplings are also evaluated in detail, which are in good agreement with the above qualitative mechanism. This work provides detailed information and insight for understanding the stacking‐dependent interlayer magnetism, which is beneficial for the application of 2D magnetic materials. [ABSTRACT FROM AUTHOR]

Single crystals of Hg1–хCdxCr2Se4 solid solutions with the normal spinel structure have been prepared via thermal annealing and characterized by X-ray microanalysis. Thermal annealing is a viable alternative to a previously proposed method: flux growth with CdCl2 as a solvent. Doping of the solid solutions with gallium and/or gallium selenide has been shown to ensure a considerable increase in the Curie temperature of the material. [ABSTRACT FROM AUTHOR]

This article focuses on a 10 at.% Mn-doped In2O3 magnetic semiconductor. A pyrophoric reaction is adapted for synthesis of the (In0.9Mn0.1)2O3 nanocrystalline dilute magnetic semiconductor (DMS). The single-phase cubic bixbyite nanocrystalline structure of Mn-doped indium oxide is determined from x-ray diffraction (XRD) and scanning electron microscopy (SEM). Investigation of temperature variation of magnetization shows a phase transition from ferromagnetic to paramagnetic at 830 K. The effective paramagnetic moment (μeff) ~ 2.32 μB/formula unit is evaluated from the inverse susceptibility [χ−1(T)] versus temperature plot. Indirect exchange interaction is mediated by spin-polarized (delocalized) conduction band electrons between two localized spins of magnetic ions (Mn3+), leading to ferromagnetism in the specimen. The optical absorption spectrum provides information about the direct allowed band gap (Eg) of (In0.9Mn0.1)2O3 nanocrystalline magnetic semiconductor which is estimated as 4.12 eV. Enhancement of the optical band gap (Eg = 4.12 eV) obtained from the optical absorption spectrum is most likely due to the quantum confinement effect of the nanocrystalline system. [ABSTRACT FROM AUTHOR]

Realization of a magnetization reversal by an external electric field is vital for developing ultra-low-power spintronic devices. In this report, starting from energy band engineering, a general design principle is proposed for achieving electrical manipulation of a nonvolatile 180° magnetization reversal. A half semiconductor (HSC) and a bipolar magnetic semiconductor (BMS) are selected as the model of magnetic layers, whose conduction-band minimum and valence-band maximum are in the same and opposite spin states, respectively. Based on the analysis of virtual hopping and tight-binding models, the interlayer coupling of HSC/insulator/BMS devices is successfully tuned between ferromagnetic and antiferromagnetic interactions by varying electric field directions. Moreover, the interlayer coupling nearly disappears after removing the electric field, proving the nonvolatile magnetization reversal. Using first-principles calculations, the feasibility of present design strategy is further confirmed by a representative device with the structure of CrBr3/h-BN/2H-VSe2. This design guideline and physical phenomena may open an avenue to explore magnetoelectric coupling mechanisms and develop next-generation spintronic devices. [ABSTRACT FROM AUTHOR]

Magnetic semiconductors with Curie temperatures higher than room temperature show potential for developing spintronic devices with combined data processing and storage functions for next-generation computing systems. In this study, we present an n-type Co19.8Fe8.6Nb4.3B6.0O61.3 magnetic semiconductor with a high Curie temperature of ∼559 K. This magnetic semiconductor has a room-temperature resistivity of ∼2.10 × 104 Å cm and a saturation magnetization of ∼76 emu/cm3. The n-type Co19.8Fe8.6Nb4.3B6.0O61.3 magnetic semiconductor was deposited on p-type silicon to form a heterojunction, exhibiting a rectifying characteristic. Our results provide the design principles for discovering high Curie temperature magnetic semiconductors with determined conduction types, which would play an essential role in realizing nonvolatile spin-based transistors that break free from the confines of currently established Si-based information technology. [ABSTRACT FROM AUTHOR]

We perform systematic first-principles calculations on the electronic structure of n -type magnetic semiconductor Ba(Zn $_{1-x}$ Co _x ) _2 As _2 with the facilitation of HSE06 hybrid functional. Supercells are used to consider the doping of Co atoms, and the first-principles band structures are unfolded for clarity. Based on the calculation results, magnetic states are preferred by individual Co atoms doped in Ba(Zn $_{1-x}$ Co _x ) _2 As _2 at diluted limit, and carriers are originated mainly from situations where only one Co atom exists in the nearest neighbor Zn sites out of certain doped Co atoms. The origination of carriers can be explained by the density of states and the unfolded band structure, where it is found that the scattering effects from single Co atom is small but quite large when more Co atoms are located at adjacent Zn sites. The large scattering effects of two adjacent Co atoms will alter the band structures near the Fermi-level. Carriers in Ba(Zn $_{1-x}$ Co _x ) _2 As _2 mainly originate from the As-4p orbitals, with partial contributions from the Co-3d orbitals. Our work provides new insights into the origin of the n -type carriers in magnetic semiconductors and will inspire the development of new magnetic semiconducting systems.

It has been proposed recently that 1D hybrid nanoobjects consisting of alternating double carbon chains and polycyclic carbon regions can be obtained from graphene nanoribbons of alternating width by electron irradiation. Here, based on density functional theory calculations, we show that magnetic and electronic properties of such nanoobjects can be changed dramatically by modifying the chain length and edge structure of polycyclic regions and this opens wide possibilities for spintronic applications. Nanoobjects composed of polycyclic regions with dangling bonds and even chains are found to behave as magnetic semiconductors that can generate spin-polarized currents. Band gaps of nanoobjects with odd chains change considerably upon switching between magnetic states making them promising for magnetic tunnel junctions. We also demonstrate that use of a hybrid exchange–correlation functional is important to properly describe stability of magnetic states, band gaps and synergistic effects of nanoobject components leading, for example, to magnetism in even chains. • Nanoobject properties strongly depend on chain parity and polycyclic region edges. • Nanoobjects with even chains and unsaturated edges can be magnetic semiconductors. • Nanoobjects with odd chains hold promise for magnetic tunnel junctions. • Stable magnetism in observed in odd chains and at unsaturated polycyclic region edges. • Even chains in nanoobjects can be magnetic because of non-local synergistic effects. [Display omitted] [ABSTRACT FROM AUTHOR]

Nanowires (NWs) are envisioned to be an important component of novel nanoscale electronic devices. Here, we perform atomistic simulations of coherent thermoelectric (TE) transport in free-standing ultrathin NWs of noble metals (viz. Au, Ag, Cu, Pt) cut along the [111] crystallographic direction using a non-equilibrium Greens function based first principles approach. Effect of decorating these NWs with Au or Pt atoms in an fcc environment, is also explored. Results of the calculated electronic structure show that all considered NWs, except the Pt and Pt-decorated NWs, are metallic and non-magnetic. Interestingly, Cu@Pt NW is found to be a magnetic semiconductor with an unequal band gap in ↑ − and ↓ − spin energy bands, while Pt NW and other Pt-decorated NWs (viz. Ag@Pt and Au@Pt) behave like a magnetic half-metal. To explore the TE potential of as-considered NWs, electrical conductance G , thermal conductance κ T , and thermopower S are computed in the linear response regime. Notably, the metallic NWs exhibit a quantized G. Among these, pristine NWs show a quantized value 3 G 0 up to a temperature of 200 K, while Cu@Au NW preserves its quantized value 5 G 0 even at T exceeding 300 K. In thermal transport, valence electrons make a dominant contribution to the room-temperature κ T of pristine NWs. The phononic contribution κ p h , however, goes up following decoration, with Pt-decorated NWs showing a pronounced increment (by a factor of ∼ 2). But, these NWs undergo a simultaneous reduction in the electronic contribution κ e l owing to half-metallic conduction, resulting in a net suppression of total thermal conductance κ T. Moreover, Pt-decorated NWs show a manifold enhancement in zero-bias S , with Ag@Pt exhibiting the highest value ∼ 119 μ V/K. However, S can be augmented considerably by adjusting the chemical potential μ of electrodes, and an overall best S ∼ − 890 μ V/K is found in Au NW for μ = 0. 575 eV. In this way, TE figure of merit Z T is tunable in pristine NWs over the range 1 − 3. 7. Correspondingly, the decorated NWs exhibit somewhat smaller S and Z T. Furthermore, spin-asymmetric electronic transport in Pt and Pt-decorated NWs results in net spin conductance G s and spin thermopower S s. It is found that the spin figure of merit Z s T , as high as 3.5, can be attained in Pt NW by controlling μ. Thus, noble metals NWs can be tailored for both thermoelectric and spin-thermoelectric applications. We have also investigated TE transport for the pristine NWs in the [110] direction, and found S and Z T to be comparatively much smaller. Such NWs may be useful as interconnects for low noise applications. • Thermoelectric transport in free-standing NWs of noble metals cut along the [111] direction. • Decoration of Cu NW with Pt makes it a magnetic semiconductor. • An overall best S ∼ − 890 μ V/K in Au NW for μ = 0. 575 eV. • ZT in pristine NWs over the range 1 – 3.7. • A decent Z c T ∼ 0. 48 and Z s T ∼ 0. 33 in Ag@Pt NW for μ = 0. [ABSTRACT FROM AUTHOR]

The magnetic properties of the Fe1−xAgxCr2S4 (0 < x < 0.2) solid solution were investigated in the temperature range 4–300 K in a DC field of 0.1 and 45 kOe. Fe1−xAgxCr2S4 is characterized by the transition temperature from the paramagnetic to the ferromagnetic state (Tc) and the irreversibility temperature (Tirr). The replacement of iron with silver ions in Fe1−xAgxCr2S4 leads to an increase in the Curie temperatures from 185 K (x = 0) to 216 K (x = 0.2) and Tcusp from 45 K (x = 0) to 125 K (x = 0.2). A section of the Fe1−xAgxCr2S4 magnetic phase diagram in the region under study has been constructed. The diagram reveals the following regions: paramagnetic, ferromagnetic, region of conditionally recurrent spin-glass (SG), and below 10 K a region associated with orbital ordering. [ABSTRACT FROM AUTHOR]

Oxygen in solids usually exists in an O 2- ionic state. As a result, it loses its magnetic nature of a single atom, wherein two unpaired electrons exist in its outer 2p orbitals. Here, it is shown that an unconventional stable ionic state of O - is realized in a new semiconductor material Sr 2 AlO 4 , leading to an intrinsic p-orbital ferromagnetism stable until ≈900 K. Experimental and theoretical investigations have clarified that one-fourth of the oxygen atoms in Sr 2 AlO 4 are insufficiently bonded in the crystal structure, resulting in a unique O - -state and p-orbital ferromagnetism. To date, the O - state is reported to exist only in non-equilibrium conditions, and p-orbital magnetism is only suggested in impurity bands with small ferromagnetic moments. The present work provides a new route for creating ferromagnetism in semiconductors and exploring new p-orbital physics and chemistry. In addition, the material shows elastic-mechanoluminescence that may enable unprecedented mechano-photonic-spintronics., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Over the past five years, significant progress has been made in understanding the magnetism and electronic properties of CaAl 2 Si 2 -type Eu M 2 X 2 ( M = Zn, Cd; X = P, As) compounds. Prior theoretical work and experimental studies suggested that EuCd 2 As 2 had the potential to host rich topological phases, particularly an ideal magnetic Weyl semimetal state when the spins are polarized along the c axis. However, this perspective is challenged by recent experiments utilizing samples featuring ultra-low carrier densities, as well as meticulous calculations employing various approaches. Nonetheless, the Eu M 2 X 2 family still exhibit numerous novel properties that remain to be satisfactorily explained, such as the giant nonlinear anomalous Hall effect and the colossal magnetoresistance effect. Moreover, Eu M 2 X 2 compounds can be transformed from semiconducting antiferromagnets to metallic ferromagnets by introducing a small number of carriers or applying external pressure, and a further increase in the ferromagnetic transition temperature can be achieved by reducing the unit cell volume. These features make the Eu M 2 X 2 family a fertile platform for studying the interplay between magnetism and charge transport, and an excellent candidate for applications in spintronics. This paper presents a comprehensive review of the magnetic and transport behaviors of Eu M 2 X 2 compounds with varying carrier densities, as well as the current insights into these characteristics. An outlook for future research opportunities is also provided., (© 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.)

As an antiferromagnetic material, chalcopyrite CuFeS 2 has both magnetic and semiconductor properties, which brings great prospects for the application of spintronics devices. Here, chalcopyrite CuFeS 2 nanoplates were successfully synthesized through a template mediated method. The CuFeS 2 exhibits a tetragonal phase while largely maintaining the hexagonal morphology of the CuS template, with particle sizes ranging between 90 and 120 nm. Specifically, the magnetic properties of CuFeS 2 can be tuned by varying the Fe content. The strong room-temperature ferromagnetism is attributed to the coexistence of the ferromagnetic Fe 7 S 8 and the antiferromagnetic CuFeS 2 , as well as to the unsaturated spin states of Fe on the surfaces of the nanoplates. Furthermore, the photoresponses of CuFeS 2 nanoplates were confirmed by I-V measurements under dark and light illumination. The stable photoresponse capability is attributed to its semiconductor properties. This novel room-temperature ferromagnetism and photoelectric effect promotes the development of CuFeS 2 nanoplates, and has great significance for the synthetic pathways of other ternary magnetic compounds. • CuFeS 2 nanoplates were successfully synthesized by template mediated method. • CuFeS 2 are of tetragonal phase and almost maintains the hexagonal morphology of CuS template. • CuFeS 2 exhibits room-temperature ferromagnetic property. • The stable photoresponse capability of CuFeS 2 is attributed to its semiconductor properties. [ABSTRACT FROM AUTHOR]

Oxide double perovskites (DPs) with half-filled 4f Rare-earth (RE) elements along with partially-filled 3d transition-metals (TM) are rich source of exotic spin-orbital properties. Herein, we have investigated explicitly, the structural properties, spin-orbital ground states of the bulk phases and electronic structure of the RE-double perovskites Sm 2 − x Gd x CoMnO 6 x = 0.0 , 0.5 , 1.0 , 1.5 by synthesizing high quality single-phase samples and undertaking high precision experimental measurements of the transport and magnetic properties down to 8 K. In fact, we are able to show that with Gd-substitution, it lowers the value of the magnetoresistance in Sm 2 CoMnO 6 (SCMO) and it is consistent with the observed Curie-Weiss temperature (T CW) which is lower than the observed ordering temperature (T C) upon Gd-substitution of Sm3+. Native presence of magnetic impurities (Co3+ and Mn3+) with low-spin S = 0 configurations in the SCMO vs. the nominal higher spin-state (Co2+ and Mn4+) with S = 3/2 is predicted. It essentially tunes super-exchange mechanism and relative ground states as compared to Gd 2 CoMnO 6 (GCMO). The synergy of crystal structure and electronic structure to the magnetic properties are thus, established with first-principles calculations data, employing self-consistent Hubbard U (U self) determination for both 3d- and 4f-site's electronic correlation. The computed quenched spin-moments (∼ 20–40 %) in the experimental observation at the Sm3+(4f5) and Gd3+(4f7) sites from the ideal value 10.0 μ B and 14.0 μ B per f.u. is established, respectively. It could be due to magnetic impurities in their ferri-magnetic ground state ordering (FiM3), as also confirmed from present first-principles calculations in the pristine limit. In SCMO x = 0.0 , the valence band is dominated with the RE(4 f)-orbitals along with the TM(3d)- and O(2p)-orbitals, resulting it as a charge-transfer type semiconductor, while in GCMO x = 1.5 , Gd(4 f)-orbitals are localized well below 6.5 eV from Fermi level, E F = 0 eV, resulting it as a Mott-insulator-like, mediated via 3d-3d transitions. The long-range ferro-magnetic spin-ordering ground states in SCMO is established through non-collinear spin-orbital ground states determinations. Indeed, the long-range insulating FM ordering in SCMO from combined 3d-4f-sub-lattice's magnetic interactions, but found to be broken with Gd-substitution (x = 0.5–1.5) aligning all 3d-4f site's spins into the in - plane. Observed coercive field (H C) and remanence asymmetry (M r), the nature of exchange-bias transformed from inverse to conventional type, as soon as it contains a small fraction of the Gd-substitution (x = 0.5). [Display omitted] • Accurate ground state predictions in pristine SCMO and GCMO may explain well demanding meta-magnetism and negative magnetisation in DPs. • Gd-substitution in SCMO lowers the value of magnetoresistance and it is consistent with the observed Curie-Weiss temperature (T CW) • The origin of the inverse EB and band gaps in DPs with Gd-substitute was overlooked earlier, once we take self-consistent Hubbard U in first-principles calculations. • Long-range insulating FM ordering in SCMO from the 3d-4f-sub-lattice's magnetic interactions was confirmed, but found to be broken with Gd-substitution. • Impurities causes the quenched spin-moments (about 20-40%) at the Sm3+(4f5) and Gd3+(4f7) sites deviate from the ideal value. [ABSTRACT FROM AUTHOR]

Due to the finite band gap and a ferromagnetic ground state, the CrI 3 monolayer is attracting great research interests. However, the low Curie temperature of 46 K is one of the major obstacles for spintronics applications. Here, we have investigated the magnetic properties of chlorinated CrI 3 monolayer with varying concentration of Cl. We investigated the dynamical and thermal stability by phonon dispersion and ab-initio molecular dynamic simulation. The band gap was decreasing with increasing Cl concentration and a half-metallic state is obtained at Cl concentration of 4.22 × 1014/cm2. The pristine CrI 3 monolayer had perpendicular magnetic anisotropy energy of 0.84 meV/Cr. We find that this perpendicular magnetic anisotropy energy can be even enhanced twice by chlorination. Due to the hybridization of I and Cr atom, we found the spin asymmetric density of states in the iodine atom and this strong enhancement in the magnetic anisotropy originated from asymmetric spin features in iodine atom. We propose that the chlorination can increase the Curie temperature up to 204 K and this is almost four times enhanced value. Based on these finding, we propose that the chlorinated CrI 3 system can be a promising material for spintronics applications. • Physical characteristics of Monolayer CrI 3 by using ab-initio molecular relation. • The band gap was decreasing with increasing Cl concentration and we obtained half-metallic semiconductor. • We investigated the dynamical and thermal stability by phonon dispersion. • The magnetic anisotropy energy were studied of Monolayer CrI 3. [ABSTRACT FROM AUTHOR]

TiO 2 solid solutions with Fe compositions of 6 %, 9 %, and 12 % were analyzed using multi-phase Rietveld refinement analysis for average structure and maximum entropy for electronic structure. VSM analysis showed that the 9 % and 12 % Fe doped TiO 2 compositions had a maximum magnetization of 0.3128 emu/g and coercivity of 574 Oe and 568 Oe, respectively. This confirms ferromagnetic tuning with Fe doping at or above 9 %. The MEM electron density at the bond critical points (BCP) of the apical and equatorial (Ti/Fe)–O bonds in 12 % Fe-doped TiO 2 is 1.088 e/Å3 and 0.8652 e/Å3, indicating polar covalent bond. This work primarily examines a new empirical correlation between MEM electron density and magnetic parameters. Fe: TiO 2 solid solutions have high magnetization and coercivity due to strong and identical (Ti/Fe) – O apical and equatorial polar covalent bonding, with low interstitial charge buildup at non-regular tetrahedral rutile lattice sites. [ABSTRACT FROM AUTHOR]

As a long‐standing research topic in materials physics and chemistry, magnetic materials have been receiving increasing attention for their applications in spintronic devices, such as spin field‐effect transistor and data‐storage memory. Two‐dimensional (2D) magnets are a family of emerging magnetic materials with atomically thin thickness, which can be easily integrated into heterostructural devices, providing incredible possibility for understanding 2D magnetism and great potential for applications in future ultrathin spintronic devices. Recent effort from theory, simulations and experiments has made notable progress on 2D magnets and devices, especially on 2D van der Waals materials and heterojunctions. Here theoretical advances using physical models and computational approaches on the study of new 2D magnets and devices are briefly summarized and possible directions for future investigation are extensively discussed, which may inspire growing interest on the development and applications of 2D magnets and spintronic devices. This article is categorized under:Structure and Mechanism > Computational Materials ScienceElectronic Structure Theory > Density Functional Theory [ABSTRACT FROM AUTHOR]

Utilizing both charge and spin degrees of freedom of electrons simultaneously in magnetic semiconductors promises new device concepts by creating an opportunity to realize data processing, transportation and storage in one single spintronic device. Unlike most of the traditional diluted magnetic semiconductors, which obtain intrinsic ferromagnetism by adding magnetic elements to non-magnetic semiconductors, we attempt to develop new magnetic semiconductors via a metal-semiconductor transition by introducing oxygen into a ferromagnetic Co-Fe-B metallic glass. The atomic structure and electronic structure of the Co-Fe-B-O sample are explored by using first-principles calculations. The total pair correlation functions of both the Co-Fe-B and Co-Fe-B-O samples evidence their glass structures. The bond pair and coordination number analysis together demonstrate that the oxygen addition enables the bond types to change from the dominant metallic bonding in the Co-Fe-B metallic glass to the mixture of metallic, ionic and covalent bonding in the Co-Fe-B-O oxide glass. This results in the localization of electron charge density and the opening of the band gap in the Co-Fe-B-O oxide glass. The density of states suggests the Co-Fe-B-O oxide glass is semiconducting with a band gap of about 1.7 eV, but there are intermediate energy levels in the band gap. Meanwhile, the Co-Fe-B-O oxide glass remains to be ferromagnetic. These results indicate that the Co-Fe-B-O oxide glass is a magnetic semiconductor transferred from a ferromagnetic Co-Fe-B metallic glass, which is further verified by the experimental realization of a Co-Fe-B-O magnetic semiconductor. Furthermore, our calculation results reveal that a hybridization of the 4s/4p, 3d electrons of ferromagnetic Co and Fe atoms and O 2p electrons exists. Such s, p-d exchange interaction is essential to bridge the mutual interaction between the electrical conduction arising from s-like electrons and ferromagnetism supported by 3d electrons in magnetic semiconductors, thereby enabling the control of ferromagnetism by electrical means. Our calculation results represent an important step to gain a deeper understanding of the oxygen addition induced metal-semiconductor transition in an amorphous alloy Co-Fe-B system. We anticipate that our calculation results provide theoretical fundamentals for experimentally transferring many other ferromagnetic amorphous alloys into ferromagnetic semiconductors with attractive magnetoelectric coupling properties.

In this study, the structural and magnetic properties of Si-doped bulk and 2D AlN were systematically investigated by first-principles calculations. Si atoms prefer to substitute Al atoms in both bulk and 2D AlN under N-rich growth conditions. In bulk AlN, Si dopants exhibit a non-magnetic state, uniform distribution, and a strong anisotropic diffusion energy barrier. In contrast to that, Si dopants prefer to form a buckling structure and exhibit a magnetic moment of 1 μB in 2D AlN. At a low Si concentration, Si atoms tend to get together with antiferromagnetic coupling between each other. However, the magnetic coupling among Si atoms changes to ferromagnetic coupling as Si concentration increases, due to the enhanced exchange splitting and delocalized impurity states. At the extreme doping limit, monolayer SiN, along with its analogs GeN and SnN, is a ferromagnetic semiconductor with a large band gap and high Curie temperature. These results indicate that 2D AlN doped by group IV atoms has potential applications in spintronic devices.

Ab initio calculations of the electronic and thermodynamic properties for the oxide ferrocobaltite of the perovskite-type La2FeCoO6 are reported. The calculations of the band structure and density of states were carried out by means of first-principles calculations, using the formalism of the Functional Density Theory and the Plane Wave and Pseudopotential method through the VASP code. Exchange and correlation energy were described using the Generalized Gradient Approximation, including spin polarization and Hubbard potential correction due to the presence of Fe-3d and Co-3d orbitals. The semiconductor behavior of the material was established by obtaining a band gap of 2.35 eV. Strong hybridizations between the 2p oxygen orbitals in the valence band with Fe2+-3d and Co4+-3d states allow us to explain the ferromagnetic nature through the superexchange mechanism between high-spin states of Fe2+ with low-spin states of Co4+ mediated by O2− orbitals. The dependence of specific heat with respect to temperature and pressure, as well as the coefficient of thermal expansion, the Debye temperature, and the Grüneisen parameter, were calculated from the equation of state, using the quasi-harmonic Debye model. The theoretical results obtained are comparable with the experimental values obtained in the literature for this material reported as a ferromagnetic semiconductor. [ABSTRACT FROM AUTHOR]

Detailed dynamic magnetic susceptibility measurements for Fe1 –xAgxCr2S4 (x = 0–0.15) solid solutions have shown that polycrystalline silver-doped iron thiochromite undergoes paramagnetic-to-ferrimagnetic phase transitions with transition temperatures dependent on the degree of silver substitution for iron, TC = 194–212 K at x = 0.05–0.15, and spin glass transitions at Tf = 80–115 K for x = 0.05–0.15. The increase in the transition temperatures with increasing silver concentration is attributable to the diamagnetic dilution effect. The cusp observed around 50 K, due to the low-temperature structural anomaly in the Fe1 –xAgxCr2S4 solid solutions, has been confirmed by measuring the imaginary part of their dynamic magnetic susceptibility as a function of temperature, χ''(T), at an increased field modulation amplitude of 15 Oe. An effect related to long-range orbital ordering as a consequence of a Jahn–Teller transition has been found at temperatures TOO = 10–15 K. [ABSTRACT FROM AUTHOR]

The choice of materials appropriate for the fabrication of waveguides and other components is the most important problem in the development of THz plasmonics. We consider the suitability of the use of In 2 - x Cr x O 3 magnetic semiconductor as a constitutive material for producing nanowires supporting propagation of the transverse magnetic (TM) and transverse electric (TE) modes of surface plasmons. We utilize the feature of this material to behave as a homogeneous low-loss negative refractive index medium existing due to the coexistence of the magnon and plasmon oscillations. The cut-off conditions of the fundamental TM 0 and TE 0 modes of the waveguide are defined. It is demonstrated that the TE 0 mode of surface plasmons has low-frequency and high-frequency cut-offs and can be propagated over a large distance (up to several hundred micrometers) with acceptable mode confinement. [ABSTRACT FROM AUTHOR]

The structural, electronic, magnetic, thermoelectric and thermodynamic properties of Ba3MnNb2O9 have been investigated using the full-potential linearized augmented plane wave method. Besides, the thermodynamic properties of the materials of interest have been studied using the quasi-harmonic Debye model accommodating the lattice vibrations effects. A comparison between the computed crystal structure parameters and the corresponding experimental counterparts shows a very good agreement between them. The band structures (BS) and density of states (DOS) ensure the magnetic semiconductors nature of the studied complex perovskite. Moreover, the thermoelectric properties of this compound were studied using the transport quasi-classical theory. The effects of pressure and temperature on the studied properties are found to be highly effective in tuning some of the macroscopic properties of the compound in question.

In this work, strontium hexaferrite (SrFe _12 O _19 ) was prepared using two different methods, the solid-state reaction and the sol–gel pechini methods. In each case, the structural properties and microstructural features were analyzed in order to evaluate their influence on the photocatalytic activity of the strontium hexaferrite. In addition, the magnetic properties of each sample were also investigated. The analysis of the photocatalytic activity was done using methylene blue as a test dye. The results show that the fabrication method significantly impacts how the photocatalytic activity occurs. Firstly, the bandgap energy of the sample obtained by the solid-state reaction method turned out to be smaller than that obtained by the sol–gel pechini method. This behavior was attributed to the structural differences shown between the two samples. On the other hand, particle size also has a significant effect on photochemical reactions. However, smaller particle sizes make it difficult for photons to transport in the system, resulting in reduced photocatalytic activity. In this case, better results were obtained from the sample obtained from the solid-state reaction method.

The magnetic properties of the Fe1−xAgxCr2S4 (0 < x < 0.2) solid solution were investigated in the temperature range 4–300 K in a DC field of 0.1 and 45 kOe. Fe1−xAgxCr2S4 is characterized by the transition temperature from the paramagnetic to the ferromagnetic state (Tc) and the irreversibility temperature (Tirr). The replacement of iron with silver ions in Fe1−xAgxCr2S4 leads to an increase in the Curie temperatures from 185 K (x = 0) to 216 K (x = 0.2) and Tcusp from 45 K (x = 0) to 125 K (x = 0.2). A section of the Fe1−xAgxCr2S4 magnetic phase diagram in the region under study has been constructed. The diagram reveals the following regions: paramagnetic, ferromagnetic, region of conditionally recurrent spin-glass (SG), and below 10 K a region associated with orbital ordering.

• Electronic and magnetic properties of Fe-doped chalcopyrite-type ZnSnAs 2 semiconductors by DFT calculations. • Magnetic exchange interaction between two Fe atoms substituting Zn and Sn sites in the supercell with different geometries. • The occupation of Sn sites by Fe atoms prefers the ferromagnetic state. • Magnetic chalcopyrites have potential as promising materials in spintronic applications. The electronic and magnetic properties of Fe-doped ZnSnAs 2 within chalcopyrite structures have been studied by first-principles calculations using the density functional theory (DFT) full-potential linearized augmented-plane-wave method and the plane-wave pseudopotential methods. The band gap of ZnSnAs 2 was determined to be 0.816 eV using the modified Beck-Jonson (mBJ) exchange potential. When Fe dopants substitutionally replace Sn atoms, half-metallic ferromagnetism is observed in ZnSnAs 2 where in the spin-down band at the Fermi level is entirely unoccupied. The magnetic exchange interaction between two Fe atoms substituting Zn and Sn sites in the supercell with different geometries has been studied. The total energy difference (ΔE) between the antiferromagnetic (AFM) and ferromagnetic (FM) configurations suggests that Fe atom occupation of Zn sites in ZnSnAs 2 leads to a predominantly AFM state, while the Fe atom occupation of Sn sites prefers the FM state. [ABSTRACT FROM AUTHOR]

Magnetic semiconductors have the potential to push the boundaries of emerging technologies like spintronics. They could change the way we process and store data by leveraging not just the electron charges, but also their intrinsic spin. Materials with low dimensionality, specifically one- or two-dimensional materials, are key to this advancement. Within this category, one-dimensional semiconductors with either antiferromagnetic or ferromagnetic properties are particularly interesting for their electronic and magnetic properties. However, creating and maintaining stable ferromagnetic ordering in these semiconductors is not straightforward. There are significant challenges, such as issues due to the disorder of dopants in dilute magnetic semiconductors, or stability problems in two-dimensional magnetic materials like chromium triiodide (CrI 3). In this work, we show a potential solution in VS 4 nanowires, a one-dimensional material found in patronite minerals. These nanowires can have four magnetic orderings: two antiferromagnetic (AFM1 and AFM2), one ferrimagnetic (FI), and one ferromagnetic (FM) ordering, which we can access using different strains. We observe two magnetic phase transitions with strains in the plastic (non-linear) regime. The nanowire transitions from AFM1 to AFM2 with ɛ z = 6. 8 %, and from AFM2 to FM with ɛ z = 11. 8 %. This ability to tune the magnetic phases in a semiconductor material opens up a vast range of opportunities for their integration into spintronic devices. We believe that the range of magnetic phases in a one-dimensional semiconductor, like VS 4 nanowires, could lead to the enhanced control of both charge and spin in nanotechnology devices. • One-dimensional exfoliable material from bulk, including from the mineral Patronite. • An antiferromagnetic semiconductor with an indirect band gap of 1.22 eV. • Magnetic phase transitions with the application of strain. • Ferromagnetic semiconductor for high strains in the plastic regime. [ABSTRACT FROM AUTHOR]

Advances in room temperature ferromagnetic semiconductors increase the opportunity to commercialize full spintronic devices. The manipulation of electron spin in semiconductor materials has driven significant research activity with the goal of realizing their amazing technological potential. Coupling of magnetic and semiconducting properties could lead to a new generation of information and communication devices. During the past 20 years, the intensive research on magnetic semiconductor materials has led to discovery of two interesting facts. Room temperature ferromagnetism is observed in undoped semiconductor oxides with empty or completely filled d- or f-orbitals, and nonmagnetic dopants can induce or enhance the room temperature ferromagnetism in nonmagnetic semiconductor materials. The organized review which addresses this phenomenon and covers the large number of studies on this subject is rare. In this study, we firstly review the advantages aspects of spintronic devices as well as the materials suitable for these applications. Here, we tried to provide a systematic study on defects induced by room temperature ferromagnetism in undoped semiconductor oxides as well as the impact of nonmagnetic dopants on ferromagnetism. We hope this review assist researchers in creating a complete picture to develop future research activities to access innovative technological applications. [ABSTRACT FROM AUTHOR]

This paper reports on the experimental findings of ac conductivity as determined from the measurement of conductance by using the Waynekerr 6500B impedance analyzer for the stoichiometric and non-stoichiometric manganese doped cobalt ferrite nanoparticles. In the dispersion of ac conductivity over the frequency band 100 Hz–1 MHz, two distinct conductive bands 100 Hz–1 kHz and 1 kHz–1 MHz for stoichiometric compositions, and 100 Hz–3 kHz and 3 kHz–1 MHz for non-stoichiometric compositions are observed. On the other hand, well-resolved peaks are observed in the dispersion of ac conductivity over the frequency band 1–120 MHz that corresponds to the hopping resonance for both the compositions. The ac conductivity is found to be tunable by the Mn content and selectable by the frequency between cutoff frequencies for both the compositions. A comparatively higher magnitude of ac conductivity is observed for the representative sample of non-stoichiometric composition and a lower magnitude for the stoichiometric compositions. The presence of tunability of ac conductivity in the studied samples is, therefore, a concern on which basis, the Joule’s heat and Joule’s heat per unit time have been determined for the studied samples by using the usual formula and also found to be tunable by the manganese content. This tunability of the generated Joule’s heat may make these possible to use in the temperature switching/sensing, and/or thermoelectric/thermomagnetic devices.

We have synthesized Fex(Cu0.5In0.5)1– xCr2S4 solid solutions and measured their magnetic properties in the temperature range 4.2–300 K in a static magnetic field of 0.1 and 45 kOe. The main magnetostatic parameters of the synthesized materials have been determined: saturation magnetization, effective and spin magnetic moments, Curie and Néel temperatures, Curie constants, and Curie–Weiss constants. The results thus obtained, including the properties of magnetic clusters and the composition dependence of the asymptotic Curie temperature, have been interpreted using a previously reported magnetic phase diagram of the Fex(Cu0.5In0.5)1– xCr2S4 solid solutions, which provides insight into the nature of the phase transformations involved. [ABSTRACT FROM AUTHOR]

Single crystals of chalcogenide chromium spinel CdCr2S4 (ferromagnet, TC ≈ 80 K) have been grown from a solution in a melt. The morphology, local elemental composition, and microstructure elements of the crystals are studied by scanning electron microscopy. All crystals have a composition close to stoichiometric. A study of their magnetic properties in the temperature range of 5–300 K in a constant (100 Oe) and/or alternating (100, 1000, and 10000 Hz) magnetic field show that CdCr2S4 has a number of features that are considered a hallmark of spin glasses. [ABSTRACT FROM AUTHOR]

Spintronics is a promising technology which aims to solve the major problems existing in today's conventional electronic devices. Realistically, this technology has the ability to combine the main functions of the modern semiconductor microelectronics and magnetic storage devices in single chip. Electrons have two fundamental degrees of freedom (DOF) called charge and spin. Conventional electronic devices used only the charge of electron for information processing using binary bits 0 and 1. The continuous developments in the conventional electronics are basically depending on reducing component size (transistors, capacitors, etc.) embedded in integrated circuits (random access memory, microprocessor, etc.). In 2019, the actual size of the transistor placed in commercial microprocessor is about 50 nm with gate length of 20 nm and node of 7 nm fabricated using TSMC's 7-nm FinFET (Taiwan Semiconductor Manufacturing Company 7-nm Fin Field Effect Transistor). The progress in the electronic devices will come to the end when the transistor node size reaches to 1 nm. Below this size, the fabrication, writing, and reading processes will be difficult or impossible due to quantum size effect. Spintronics is the alternative future technology, which is based on using the fundamental spin of electron in additions to its charge to carry and store information. Transfer from conventional electronics to spintronics technology opens the possibilities to construct devices with high storage density, low power consummation, and fast operation and that are cheap and robust. The main aim of this work is to give a simple and clear picture to researchers who are beginners of research in this field. In this review, basic outlines of spintronics technology and its fundamental properties were discussed. Here, we highlight two groups of materials strongly candidates to fabricate spintronics devices, denoted diluted magnetic semiconductor and multiferroic materials. [ABSTRACT FROM AUTHOR]

We have synthesized Fe1 –xAgxCr2S4 (0 < x < 0.5) solid solutions via doping of the FeCr2S4 thiochromite with silver. From a break in the composition dependence of the unit-cell parameter for the synthesized materials, the solid solution series has been shown to be limited by x = 0.22. The magnetic properties of the solid solutions have been studied at temperatures from 4 to 300 K in a magnetic field H = 3980 A/m (50 Oe). All of the materials have been shown to be ferrimagnets with a Curie temperature rising with silver concentration: from 185 K at x = 0 to 203 K at x = 0.22. We have determined saturation magnetic moments of the solid solutions and proposed a model that accounts for their observed magnetic properties. [ABSTRACT FROM AUTHOR]

Thermoelectric thin films are candidate materials that can be used to supply the energy harvested to autonomously power Internet of Things (IoT) sensors and devices. This work deals with the fabrication of chromium silicide thin films and the characterization of their thermoelectric properties. The films were grown by utilizing a high-temperature molecular beam epitaxy (MBE) apparatus under different conditions. The highest power factor of more than 0.6 mW/m K2 was obtained for the chromium silicide film deposited at a temperature of 900 °C. The thermal conductivity of the thin film was observed to be approximately one-third that of bulk CrSi2. [ABSTRACT FROM AUTHOR]

The magnetic susceptibility of the ferrimagnet FeCr2S4 was studied by a dynamic method in order to highlight the nature of a magnetic transition in the region of T = 60 K. The properties of the compound were measured in zeroth DC magnetic field НDC = 0 in the temperature range 4–230 K at the modulation amplitudes НАC = 1 and 17 Oe and the AC frequencies ν = 10, 100, 1000, and 10 000 Hz. At T > 60 K, the properties of FeCr2S4 correspond to the long-range ferrimagnetic order with local spin disorder. Spin lattice distortions (microareas or magnetic clusters) strongly increase in the region of 150 K, where a local spin glass appears with the spin freezing temperature Tf = 155 K. The flat maximum of the impurity spin glass in FeCr2S4 at T = 155 K can be considered as a mere assembly or conglomerate of especially large magnetic clusters with the effective Curie temperature T = 155 K. [ABSTRACT FROM AUTHOR]

Magnetic properties of Fex(Cu0.5In0.5)1– xCr2S4 (x = 0.6–1) solid solutions between ferrimagnet FeCr2S4 (TC = 170 K) and antiferromagnet Cu0.5In0.5Cr2S4 (TN = 28 K) have been studied at temperatures in the range 4–300 K in permanent magnetic fields H = 7 960 A/m (100 Oe) and 3.58 × 106 A/m (45 kOe). Magnetic transition temperatures have been determined. The divergence between ZFC and FC curves below the magnetic ordering temperature has been observed for all compositions. An Fe0.7Cu0.15In0.15Cr2S4 sample has the highest coercive force. The interpretation of results is based on the account for the system's coercivity and the domain wall pinning in the test samples by nonmagnetic copper and indium ions. [ABSTRACT FROM AUTHOR]

We report on the successful spin injection from EuS/Co multilayers into (100) GaAs at low temperatures. The spin injection was verified by means of polarized electroluminescence (EL) emitted from AlGaAs/GaAs-based spin-light-emitting diodes in zero external magnetic field. Spin-polarized electrons were injected from prototype EuS/Co spin injector multilayers. The use of semiconducting and ferromagnetic EuS circumvents the impedance mismatch. The EL was measured in side emission with and without an external magnetic field. A circular polarization of 5% at 8 K and 0 T was observed. In view of the rather rough interface between the GaAs substrate and first EuS layer, improvement of the interface quality is expected to considerably enhance the injected electron spin polarization. [ABSTRACT FROM AUTHOR]

• The structure shrinkage at (001) direction exhibits orbitals scalene ellipsoidal shape leading to PMA of ∼(664 ± 25) µeV. • The L 2,3 -edges of Mn atoms are performed with the aim of the understanding the orbital hybridizations and its link with spin moment orientations. • The zero in sum of symmetric XMCD spectrums for spin (up/down) conspicuously ascertains significant antiferromagnetic behavior. • The XMLD spectrum confirms the perpendicular orientation of easy magnetization axis. We have used the full potential linearized augmented plane waves (FP-LAPW) method to investigate the magnetic properties of Zn 0.50 Mn 0.50 S/Rh (001) system. Spin-orbit coupling and different spin-polarized states for the electronic structure are considering in LSDA potential. The L 23 -edges X-ray absorption (XAS) and X-ray magnetic dichroism (XMD) are calculated locally at Mn–Mn sites. The results show no circular dichroism spectra (leading to zero in sum for a spin up and spin down conspicuously of the independent Mn atoms), which is a behavior specific to an antiferromagnetic material. The system shows a perpendicular magnetic anisotropy of (664 ± 25) µeV. Hence, the magnetic moments are arranged antiparallel and reach the value of ±3.72 µ B especially between nearest neighbor Mn atoms. This can be explaining by a large number of d-electrons available to be spin-polarized in the low-dimensional regime. We propose that the magnetic properties are resulting from the hybridization between Mn–d and sulfur–p states at a given distance. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Highlight • We investigate the effect of doping acceptor impurity nitrogen (N) in (Zn,Fe)Te. • The changes in structural and magnetic properties due to N-doping are correlated. • Magnetic properties change from paramagnetism to ferromagnetism due to N-doping. • Magnetic properties turn back to paramagnetism at higher N concentration. • Change of magnetism reflects change of Fe valence state and extrinsic precipitates. Abstract We have investigated the effect of co-doping of nitrogen (N) acceptor impurity on the structural and magnetic properties of (Zn,Fe)Te. We grew (Zn,Fe)Te:N thin films by molecular beam epitaxy (MBE) with a fixed Fe composition 1.5% and varied N concentrations in the range of [N] = 8 × 1017– 4 × 1019 cm−3. Structural analyses by using x-ray absorption fine structure (XAFS) and transmission electron microscope (TEM) reveal that N-doped films with intermediate N concentration [N] = 8 × 1017– 7 × 1018 cm−3 are mainly composed of pure diluted phase with substitutional Fe atoms in the valence state deviated from Fe2+, while Fe is dominantly incorporated in an Fe-N compound at the highest N concentration [N] = 4 × 1019 cm−3. Accordingly, the magnetization measurement using SQUID confirms a drastic change of magnetic properties; a linear dependence of magnetization of magnetic field (M-H), typical of van-Vleck paramagnetism in the film without N-doping changes into ferromagnetic behaviors with a hysteretic M-H curves at the intermediate N concentrations and comes back to a linear M-H dependence at the highest N concentration. The ferromagnetism in the intermediate [N] range may reflect a deviation of the valence state of the substitutional Fe from Fe2+, while the linear M-H at the highest [N] would be attributed to precipitates of an Fe-N compound. [ABSTRACT FROM AUTHOR]

We have studied the magnetic properties of Cd1 –xFexCr2S4 solid solutions in the FeCr2S4–CdCr2S4 system in the range 0.6 ≤ x < 1. Measurements were made in the temperature range 5–300 K in static (≤7960 A/m) and ac (10, 100, and 1000 Hz) magnetic fields of 79.60 A/m peak. All of the materials have been shown to exhibit low-temperature magnetic anomalies due to the effect of orbital ordering in FeCr2S4, a basic component, at 10 K. [ABSTRACT FROM AUTHOR]