High perpendicular magnetic anisotropy (PMA), a property needed for nanoscale spintronic applications, is rare in oxide conductors. We report the observation of a PMA up to 0.23 MJ/m 3 in modestly strained (-0.3%) epitaxial NiCo2O4 (NCO) films which are room-temperature ferrimagnetic conductors. Spin-lattice coupling manifested as magnetoelastic effect was found as the origin of the PMA. The in-plane x 2 -y 2 states of Co on tetrahedral sites play crucial role in the magnetic anisotropy and spin-lattice coupling with an energy scale of 1 meV/f.u. The elucidation of the microscopic origin paves a way for engineering oxide conductors for PMA using metal/oxygen hybridizations. sin( ) cos( ) = [sin 2 ( ) − sin( ) cos( )], with 127, the spherical angles of magnetization, and the angle between magnetization and anisotropy axis. As 128 the anisotropy scale K increases, the magnetization direction of minimum energy tilts further from the field 129 direction and more towards the anisotropy axis. 131A consequence of the relative orientations of the laser incidence and magnetization is that a large enough 132 misalignment of the directions leads to a flipping of the sign of the magneto-optic effect. Explicitly, 133̂′ ⋅̂= 0 when the angle of incidence satisfies tan( ) = , and on either side of this value, the effect of 134 the magnetization switches signs. This is displayed visually in the supplementary Fig S3(a)-(d). The severe 135 misalignment of the laser k'-vector and magnetization direction seen in the NCO/MAO(111) measurements 136 leads directly to the emergence of inverted hysteresis loops, and the three-fold rotational symmetry of the 137 angle-dependent MOKE measurement. 139We can further analyze the effect of magnetization direction relative to incidence direction modeling the 140 Magneto-optic Kerr Effect in terms of the Lorentz force experienced by charges in the magnetized 141 material. In our case of s-polarized light (i.e. polarization perpendicular to the plane of reflection), the 142 electric field forces an oscillation of the charges, which then experience a Lorentz force. With light 143 polarization along the x-axis (i.e. s-polarized light), charges will be forced to oscillate along this same 144 axis. Given the most general magnetization direction ̂= ( , , ), the force experienced will be
Recent discovery of a new class of materials, spin-gapless semiconductors (SGS), has attracted considerable attention in the last few years, primarily due to potential applications in the emerging field of spin-based electronics (spintronics). Here, we investigate structural, electronic, and magnetic properties of one potential SGS compound, MnCrVAl, using various experimental and theoretical techniques. Our calculations show that this material exhibits ≈ 0.5 eV band gap for the majority-spin states, while for the minority-spin it is nearly gapless. The calculated magnetic moment for the completely ordered structure is 2.9 μB/f.u., which is different from our experimentally measured value of almost zero. This discrepancy is explained by the structural disorder. In particular, A2 type disorder, where Mn or Cr atoms exchange their positions with Al atoms, results in induced antiferromagnetic exchange coupling, which, at a certain level of disorder, effectively reduces the total magnetic moment to zero. This is consistent with our x-ray diffraction measurements which indicate the presence of A2 disorder in all of our samples. In addition, we also show that B2 disorder does not result in antiferromagnetic exchange coupling and therefore does not significantly reduce the total magnetic moment.
The growth of new magnetic materials on suitable insulating substrates is an important part of the development of spin-electronics devices for memory or information processing. Epitaxial thin films of Mn2PtSn were grown on a MgO [001] substrate by magnetron co-sputtering of the constituents. Structural, magnetic, and electron-transport properties were investigated. The epitaxial Mn2PtSn film has an inverse tetragonal structure with the c-axis aligned in the plane of the MgO substrate. The lattice constants determined using XRD and TEM analysis are c = 6.124 Å and a = b = 4.505 Å. The orientation of Mn2PtSn c-axis which is 45° away from the a-axis of MgO has resulted in a small lattice mismatch of about 2.8%. The measured saturation magnetization is 5.3 μB/f.u., which is smaller than the first-principles calculated value of 6.4 μB/f.u. for ferromagnetic spin arrangement. Magnetization measurements determined the bulk magnetocrystalline anisotropy constant Kv of about 11.3 Merg/cm3 (1.13 MJ/m3). The electron-transport behavior is similar to that of normal magnetic metals. These results indicate that Mn2PtSn may have promising applications in spintronic devices.
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