We have studied the charge to spin conversion in Bi 1−x Sb x /CoFeB heterostructures. The spin Hall conductivity (SHC) of the sputter deposited heterostructures exhibits a high plateau at Bi-rich compositions, corresponding to the topological insulator phase, followed by a decrease of SHC for Sb-richer alloys, in agreement with the calculated intrinsic spin Hall effect of Bi 1−x Sb x alloy. The SHC increases with increasing thickness of the Bi 1−x Sb x alloy before it saturates, indicating that it is the bulk of the alloy that predominantly contributes to the generation of spin current; the topological surface states, if present in the films, play little role. Surprisingly, the SHC is found to increase with increasing temperature, following the trend of carrier density. These results suggest that the large SHC at room temperature, with a spin Hall efficiency exceeding 1 and an extremely large spin current mobility, is due to increased number of Dirac-like, thermally-excited electrons in the L valley of the narrow gap Bi 1−x Sb x alloy.

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Epitaxial CoFe 2 O 4 /Al 2 O 3 bilayers are expected to be highly efficient spin injectors into Si owing to the spin filter effect of CoFe 2 O 4 . To exploit the full potential of this system, understanding the microscopic origin of magnetically dead layers at the CoFe 2 O 4 /Al 2 O 3 interface is necessary. In this paper, we study the crystallographic and electronic structures and the magnetic properties of CoFe 2 O 4 (111) layers with various thicknesses (thickness d = 1.4, 2.3, 4, and 11 nm) in the epitaxial CoFe 2 O 4 (111)/Al 2 O 3 (111)/Si(111) structures using soft X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) combined with cluster-model calculation. The magnetization of CoFe 2 O 4 measured by XMCD gradually decreases with decreasing thickness d and finally a magnetically dead layer is clearly detected at d = 1.4 nm. The magnetically dead layer has frustration of magnetic interactions which is revealed from comparison between the magnetizations at 300 and 6 K. From analysis using configuration-interaction cluster-model calculation, the decrease of d leads to a

Magnetic anisotropies of ferromagnetic thin films are induced by epitaxial strain from the substrate via strain-induced anisotropy in the orbital magnetic moment and that in the spatial distribution of spin-polarized electrons. However, the preferential orbital occupation in ferromagnetic metallic La 1−x Sr x MnO 3 (LSMO) thin films studied by x-ray linear dichroism (XLD) has always been found out-of-plane for both tensile and compressive epitaxial strain and hence irrespective of the magnetic anisotropy. In order to resolve this mystery, we directly probed the preferential orbital occupation of spin-polarized electrons in LSMO thin films under strain by angle-dependent x-ray magnetic circular dichroism (XMCD). Anisotropy of the spin-density distribution was found to be in-plane for the tensile strain and out-of-plane for the compressive strain, consistent with the observed magnetic anisotropy. The ubiquitous out-of-plane preferential orbital occupation seen by XLD is attributed to the occupation of both spin-up and spin-down out-ofplane orbitals in the surface magnetic dead layer.

We have investigated the orbital states of the orbital-glassy (short-range orbital ordered) spinel vanadate Co1.21V1.79O4 using x-ray absorption spectroscopy (XAS), x-ray magnetic circular dichroism (XMCD), and subsequent configuration-interaction cluster-model calculation. From the sign of the XMCD spectra, it was found that the spin magnetic moment of the Co ion is aligned parallel to the applied magnetic field and that of the V ion anti-parallel to it, consistent with neutron scattering studies. It was revealed that the excess Co ions at the octahedral site take the trivalent low-spin state, and induce a random potential to the V sublattice. The orbital magnetic moment of the V ion is small, suggesting that the ordered orbitals mainly consists of real-number orbitals.

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Spin-charge interconversion (SCI) is a central phenomenon to the development of spintronic devices from materials with strong spin-orbit coupling (SOC). In the case of materials with high crystal symmetry, the only allowed SCI processes are those where the spin-current, charge-current, and spin-polarization directions are orthogonal to each other. Consequently, standard SCI experiments are designed to maximize the signals arising from the SCI processes with conventional mutually orthogonal geometry. However, in low-symmetry materials, certain nonorthogonal SCI processes are also allowed. Since the standard SCI experiment is limited to charge current flowing only in one direction in the SOC material, certain allowed SCI configurations remain unexplored. Here, we perform a thorough SCI study in a graphene-based lateral spin valve combined with low-symmetry MoTe 2 . Due to a very low contact resistance between the two materials, we can detect SCI signals using both a standard configuration, where the charge current is applied along MoTe 2 , and a recently introduced [three-dimensional-(3D) current] configuration, where the charge-current flow can be controlled in three directions within the heterostructure. As a result, we observe three different SCI components, one orthogonal and two nonorthogonal, adding valuable insight into the SCI processes in low-symmetry materials. The large SCI signals obtained at room temperature, along with the versatility of the 3D-current configuration, provide feasibility and flexibility to the design of the next generation of spin-based devices.

The perpendicular magnetic anisotropy of a layered ferromagnetic semiconductor (Ba,K)­(Zn,Mn)2As2 is studied using angle-dependent X-ray magnetic circular dichroism (XMCD) measurements. The large magnetic anisotropy with an anisotropy field of 0.85 T is deduced by fitting the Stoner–Wohlfarth model to the magnetic-field-angle dependence of the projected magnetic moment. Transverse XMCD spectra highlight the anisotropic distribution of Mn 3d electrons, where the d xz and d yz orbitals are less populated than the d xy state because of the D 2d splitting that arises from the elongated MnAs4 tetrahedra. The magnetic anisotropy originates from the degeneracy lifting of p–d xz , d yz hybridized states at the Fermi level. Namely, spin–orbit coupling lifts their degeneracy and induces energy gain when spins align along the z direction. The present system offers another tuning knob to control magnetic anisotropy through atomic orbital engineering.