Lattice axial ratio and large uniaxial magnetocrystalline anisotropy in L1_0-type FePd single crystals prepared under compressive stress

摘要

L1_0-type FePd single crystals with a high order degree were prepared by ordering under compressive stress. Experimental and theoretical investigations on the relation among the axial ratio, d electron number and magnetocrystalline anisotropy energy (MAE) in L1_0-type FePd single crystals have been carried out. In the concentration dependence of the lattice constants, the a axis exhibits a strong dependence, compared with that of the c axis. As a result, the ratio of c/a decreases with increasing Pd concentration. The uniaxial magneto-crystalline anisotropy constant K_U at the equiatomic composition is evaluated to be 2.1 X 10~7 erg/cm~3 at 4.2 K and 1.7 X 10~7 erg/cm~3 at 300 K. The MAE becomes weaker as the ratio of c/a is apart from unity at higher Pd compositions. The calculated results by the first principles calculations with the LMTO-ASA including the spin-orbit coupling for the MAE of L1_0-type Fe_(50)Pd_(50) are in accord with the present experimental results. The increase in the d electron number due to the increase of the Pd concentration facilitates the decrease of the MAE, cooperating with the decrease in the axial ratio c/a.