title: The origin of perpendicular magneto-crystalline anisotropy in L1(0)-FeNi under tetragonal distortion.
abstract: We investigated the origin of perpendicular magneto-crystalline anisotropy (MCA) in L1(0)-ordered FeNi alloy using first-principles density-functional calculations. We found that the perpendicular MCA of L1(0)-FeNi arises predominantly from the constituent Fe atoms, which is consistent with recent measurements of the anisotropy of the Fe orbital magnetic moment of L1(0)-FeNi by means of x-ray magnetic circular dichroism. Analysis of the second-order perturbation of the spin-orbit interaction indicates that spin-flip excitations between the occupied majority-spin and unoccupied minority-spin bands make a considerable contribution to the perpendicular MCA, as does the spin-conservation term for the minority-spin bands. Furthermore, the MCA energy increases as the in-plane lattice parameter decreases (increasing the axial ratio c/a). The increase in the MCA energy can be attributed to further enhancement of the spin-flip term due to modulation of the Fe d(xy) and d(x(2) - y(2)) orbital components around the Fermi level under compressive in-plane distortion.
authors: Research Institute of Electrical Communication (RIEC), Tohoku University, Katahira 2-1-1, Sendai 980-8577, Japan. miura@riec.tohoku.ac.jp
authors: Yoshio
authors: Y
authors: Miura
authors: Sho
authors: S
authors: Ozaki
authors: Yasushi
authors: Y
authors: Kuwahara
authors: Masahito
authors: M
authors: Tsujikawa
authors: Kazutaka
authors: K
authors: Abe
authors: Masafumi
authors: M
authors: Shirai