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This study investigated the structural, elastic, electronic, thermal, magnetic, and optical behavior of GeGa 2 O 4 , FeGa 2 O 4 , GeFe 2 O 4 , and FeFe 2 O 4 spinel oxides based on ab -initio calculations. The results showed that the non-magnetic spinel oxide GeGa 2 O 4 exhibited remarkable physical properties due to Fe occupancy at different lattice sites within the spinel lattice. The Fe containing spinel oxides (FeGa 2 O 4 , GeFe 2 O 4 , and FeFe 2 O 4) were found to be stable in the magnetic phase in contrast to the host GeGa 2 O 4 spinel oxide. The spin polarizations of FeGa 2 O 4 , GeFe 2 O 4 , and FeFe 2 O 4 oxides were calculated as 98.5%, 98.4%, and 100%, respectively. Analysis of the elastic and mechanical properties showed that all of the spinel oxides followed the Born and Huang criteria for mechanical stability. The highest Debye temperature (θ D = 663.77 K) was determined for the FeGa 2 O 4 spinel oxide. For GeGa 2 O 4 , FeGa 2 O 4 , GeFe 2 O 4 , and FeFe 2 O 4 oxides, the calculated structural parameters (cation–anion bond lengths and average values of tetrahedral and octahedral radii) predicted the following cation distributions among the A and B atomic sites: (G e 2 +) [ G a 2 3 + ] O 4 − 2 , (F e 2 +) [ G a 2 3 + ] O 4 − 2 , (G e 4 +) [ F e 2 2 + ] O 4 − 2 , and (F e + 2) [ F e 2 3 + ] O 4 − 2 . The calculated electronic structures indicated that the host GeGa 2 O 4 spinel oxide and FeFe 2 O 4 spinel ferrite were semi-conducting and half-metallic ferromagnetic, respectively, whereas FeGa 2 O 4 and GeFe 2 O 4 oxides exhibited semi-metallic behavior. The GeFe 2 O 4 spinel oxide was found to have the highest saturation magnetization (185.79 emu g−1) and total magnetic moment (8.26 Σ B fu −1). The calculated optical properties indicated the suitability of these oxides for use in optical filters and sensors. The electronic and magnetic characteristics of these spinel oxides with excellent thermal and elastic stability suggest that they have potential uses in diluted magnetic semiconductor devices. [Display omitted] • Effects on physical properties of GeGa 2 O 4 with Fe occupancy are observed. • GeGa 2 O 4 , FeGa 2 O 4 , GeFe 2 O 4, and FeFe 2 O 4 spinels exhibit mechanical anisotropy. • Presence of Fe at A, B, and/or both sites reduces electronic, and optical bandgap. • GeFe 2 O 4 shows semi-metallic behavior with m t o t = 8.26 μ B /f.u and M S = 185.79 emu/g. • The oxides containing Fe have less threshold electronic transition energy. [ABSTRACT FROM AUTHOR]

This study focuses on new diluted magnetic semiconductors that have good characteristics. The chemical compound we use in this paper is Mg 1-x Cr x S (x = 0,0, 0.125, 0.25, 0.50, 0.75) at the ferromagnetic rock salt phase, We used the linearized augmented plane wave method implemented in the wien2k package to simulate compound properties and adopted the WC-GGA approximation to calculate structural and elastic properties and the Tb-mBJ approximation (Tran-Blaha modified Becke-Johnson potential) to calculate electronic, and optical properties. The results obtained prove that the ferromagnetic (FM) phase is more stable than the antiferromagnetic (AFM) and nonmagnetic (NM) phases, the energy band of all ternary compounds Mg 1-x Cr x S has been shown to be half-metals with a 100% spin polarization at the Fermi level (E F) and total magnetic moment values equal to 4 μB. The study reported that the elastic properties of Mg 1-x Cr x S (x = 0.125, 0.25, 0.50, 0.75) compounds are mechanically stable with high mechanical anisotropy. The optical spectra of ternary compounds Mg 1-x Cr x S (x = 0.125, 0.25, 0.50, 0.75) are distinguished from those of MgS by the appearance of additional absorption at low energy. The compounds are dispersive media that show strong absorption in the ultraviolet radiation region observed on the α (ω) curve. [ABSTRACT FROM AUTHOR]

We investigated magneto-electrical properties and the effect of intrinsic point defects in the lattice on film properties of 10 mol% cobalt containing ZnO thin films that were doped with 0.7 ± 0.1 to 1.1 ± 0.2 mol% W atoms. Thin films were deposited on Si (100) substrates. The anomalous Hall Effect seen in magneto-electrical measurements indicated a correlation between the polarized spins and the positive magneto-resistivity due to hole and electron mediated interactions. N-type carriers were dominant in conductivity, as shown by Hall resistance measurements. The 55 % positive magneto-resistivity and the split of 132.3 ± 0.1 Ω and 28.5 ± 0.1 Ω differences in the magneto-hysteresis curves through both negative and positive regions, respectively, proved that a polarized spin current was effectively formed under both s-d and p-d interactions. In addition, the shallow energy levels, close to extreme points of conduction and valance bands, reinforced the polarized spin current. [ABSTRACT FROM AUTHOR]

The spin-polarized electronic band structure calculations are carried out to theoretically investigate the effect of anti-site disordering to the electronic band structure and magnetic properties of LiMgPdSb-type CoFeTiAl alloy. We found that the Co–Ti and Fe–Ti antisite disordering can induce the diluted magnetism in CoFeTiAl alloy. Especially, the Fe–Ti antisite disordering can induce a 100% spin polarization at the Fermi level at a certain degree of anti-site disordering. The Co–Fe antisite disordering is easy to occur in CoFeTiAl alloy but has little effect on the semiconductive characteristic and magnetic properties. The Co, Fe and Ti atoms at the anti-site contribute the magnetization in CoFeTiAl alloy. The diluted magnetism in CoFeTiAl alloy can be induced by the anti-site disordering instead of the introduction of magnetic dopant elements. [ABSTRACT FROM AUTHOR]

The presence of spin polarization in Mn-doped ZnO thin film is very important for spintronic applications. Spin polarization was detected using simple method. This method depends on measuring the optical transmittance using circular polarized light in visible and near infra-red region. It was found that, there is a difference in the optical energy gap of the film for circular left and circular polarized light. For temperatures > 310 K the difference in energy gap is vanished. This result is confirmed by measuring the magnetic hysteresis of the film. This work introduces a promising method for measuring the ferromagnetism in diluted magnetic semiconductors. [ABSTRACT FROM AUTHOR]

Spin polarized van der Waals (vdW) heterostructures have attracted considerable interest owing to the spin splitting manipulation. In this paper, first-principles calculations are employed to explore the two-dimensional arsenene/CrI 3 vdW heterostructure as a promising spin polarized material, as well as the spin polarization under strain and electronic field are investigated. The most stable stacking configuration and ferromagnetic (FM) property of the arsenene/CrI 3 vdW heterostructure have been confirmed. The detailed calculations show that the Curie temperature (T c) of the FM coupling CrI 3 layer in the heterostructure can be enhanced up to 61 K, which is attributed to both superexchange interaction and proximity exchange effect. The electronic structures suggest that this heterostructure possess an intrinsic type-II band alignment and diluted magnetic semiconductor property. Interestingly, we found a transition from diluted magnetic semiconductor to half-metal and gradually to metal induced by the biaxial strains, and the extra electronic field can modulate the "maxican hat" of the valance band maximum (VBM) of arsenene. Our work provides not only application prospects of the arsenene/CrI 3 vdW heterostructure nanodevices but also theoretical effective support for the research and development of the spin electronics and flexible electronics. • The arsenene/CrI 3 heterostructure possess an intrinsic type-II band alignment and diluted magnetic semiconductor property. • Biaxial strains can make arsenene/CrI 3 heterostructure transform from diluted magnetic semiconductor to half-metal and gradually to metal. • Electronic field can change the contribution of As and I atoms in VBM, enlarge the band gap. [ABSTRACT FROM AUTHOR]

In search of d 0 magnetism, the magnetic behavior of SnO 2 with cation substitution from group1A (Li, Na, K) and group 2A (Be, Mg, Ca) elements has been systematically studied using Density Functional Theory (DFT). While an impurity from group 1A elements switches on ferromagnetism at a lower concentration itself, sufficient hole density is required for a group 2A impurity to create a spontaneous spin polarized ground state, a finding that has not been reported in earlier investigations. Our DFT results predict for the first time that impurities from group 2A (Mg, Ca) in SnO 2 can promote room temperature ferromagnetism. Further, the emergence of ferromagnetism due to doping from group 1A elements, which injects three holes per defect, has been mapped successfully onto a modified Hubbard model from the literature. Doping of a single Na atom in the supercell (concentration 6.25 at%) makes the system ferromagnetic, with a magnetic moment close to 3.0 μ B per defect, and a Curie temperature of 815 K, obtained in the mean field approximation. This agrees closely with a model prediction of 750 K. Finally, the triggering of ferromagnetism by an impurity atom from group 2A, which adds two holes per defect in the system, implies that the prescription of three holes per defect given in the literature is not a necessary criterion for hole induced ferromagnetism. Rather, the analysis of the density of states and ferromagnetic coupling indicate that the system needs a critical hole concentration to activate ferromagnetism, by pushing the Fermi level inside the valence band in order to satisfy the Stoner criterion. [ABSTRACT FROM AUTHOR]

A modification of Blonder–Tinkham–Klapwijk (BTK) model is proposed to describe transport properties of diluted magnetic semiconductor (DMS)/superconductor(SC)/DMS double tunneling junctions. Coherent spin-polarized transport is studied by taking into account the Andreev reflection on spatial variation of SC barrier parameters in the heterostructure. It is shown that the conductance spectrum exhibits an oscillatory behavior with quasi-particle energy, and the oscillation amplitude is reduced with increasing temperature. We also examine the dependence of tunneling magnetoresistance (TMR) on the barrier strength ( κ ) and spin polarization ( P ) of two DMS layers. Our results show that TMR decreases with increasing temperature and barrier strength, which may be useful in designing the nano spin-valve devices based on DMS and SC materials. [ABSTRACT FROM AUTHOR]

Determining the atomic origin of magnetism in non-magnetic elements doped dilute magnetic semiconductors (DMS) is a key issue to understand the room temperature ferromagnetism. Here, using electron magnetic circular dichroism (EMCD), an element-selectivity and high spatial resolution technique, we provide unambiguous experimental evidence: spin polarization of carbon atoms contributes to the local magnetic moments of Al-doped 4H–SiC DMS. The result is further confirmed by first-principle calculations. [ABSTRACT FROM AUTHOR]

In the present work, theoretical investigations of structural, electronic, magnetic, and thermoelectric properties of Cd 0.875 TM 0.125 O (TM = Mn, Fe, Co, Ni) half-metallic ferromagnets are done using WIEN2K code. The computed results when compared with the reported theoretical works reveal consistency. The band structures for spin up (↑), and spin down (↓) channels reveal the half metallic (Mn, Co, Fe), and frustrated (Ni) magnetism. The nature of magnetism has been analyzed in terms of hybridization among 3d states of TMs, individual Cd (5s, 4d) states, and O (2p) states. The control and function of the electron spin are revealed by calculating exchange energies (Δ x (d), Δ x (pd)), crystal field energy (ΔE cryst) and exchange constant (N o α, N o β), those play a very crucial role in understanding the magnetic nature. Moreover, double exchange and RKKY models are discussed to justify the observed half-metallic, and metallic behaviors, which are responsible for the magnetic moments to stabilize a magnetic polarization. The influence of electron spin is explained using the computed electrical and thermal conductivities, while thermoelectric power is elaborated by computing Seebeck coefficient and power factor. • Above room temperature ferromagnetism, and spintronic applications •Quantum spin of electrons dominant the charge with multifuctional properties •Exchange mechanism certifies the ferromagnetism by electron spin instead of magnetic ion clustering •Half metallic ferromagnetism and 100% spin polarization •Large value of electrical conductivity and ultralow low values of thermal conductivity. [ABSTRACT FROM AUTHOR]

Using ab initio numerical results, we present a quantitative verification of the proposed contribution to the magnetic coupling in diluted magnetic semiconductors and transition metal oxides originated via successive spin polarizations over dopants and their first nearest neighboring (1nn) anion ligands. This is achieved through an examination of the variation with the magnetization density of both the magnetic moments of 3-d transition metal dopants and those of their 1nn anion ligands in various hosts. These results are then used to derive approximate exchange coupling constants assigned to the magnetic coupling between a dopant and its first nearest neighbor anion ligands for each host-dopant pair. This allows us to justify and/or predict the spin polarization state of an anion ligand which is common to two or three magnetic dopants and, in turn, to justify and/or predict the spin configuration and the intercoupling (ferromagnetic and/or antiferromagnetic) among the atoms of a cluster of dopants sharing common anion ligands. [ABSTRACT FROM AUTHOR]

• The proximity effect of graphene effectively improves the mobility and Curie temperature of the composite system. • There is a significant charge transfer at the interface between graphene and (V, N)ZnO. • The (V, N) doping pair on the surface of ZnO induces spin polarization of the graphene. Oxide-based diluted magnetic semiconductors usually exhibit above room-temperature ferromagnetism, but low carrier mobility limits their applications in novel spintronics. In this study, using first-principles calculation, the mobility, electronic and magnetic properties of V-N codoped ZnO((V, N)ZnO) system and its composite system (V, N)ZnO/graphene are studied. Compared with (V, N)ZnO, our results show that the electron mobility of the composite system is obviously increased by about three times (from 500 cm2 V−1 s−1 to 1500 cm2 V−1 s−1). In addition, we find that the ferromagnetism of the composite system is largely enhanced than that of the only V-N codoped ZnO. The Curie temperature of the composite system is estimated to be about 630 K based on the mean-field approximation theory, which is nearly twice as high as the (V, N)ZnO(321 K). This study provides effective theoretical guidance for improving carrier mobility and Curie temperature of oxide based dilute magnetic semiconductors. [ABSTRACT FROM AUTHOR]