Effect of structural strain on magnetic anisotropy energy of each element in alternately layered FeNi thin films

Structure and magnetic anisotropy of alternately layered FeNi thin films grown on Ni (x = 3-21 ML)/Cu(001) are investigated by means of reflection high-energy electron diffraction (RHEED) and x-ray magnetic circular dichroism (XMCD). From the RHEED analysis, we find that n ML FeNi films grow with a similar in-plane lattice constant, a, to that of Cu up to the total film thickness, n + x, of similar to 13 ML, from which the decrease in a occurs. For the Ni-sandwiched Fe layer, we find from the XMCD analysis that the perpendicular component of the orbital magnetic moment increases and the in-plane component decreases as the in-plane lattice constant gets smaller. This suggests that perpendicular magnetic anisotropy is enhanced when the compressive strain in the in-plane direction is applied to the Fe layer. On the other hand, in the case of the Fe-sandwiched Ni layer, the orbital magnetic moment in both directions shows a small dependence on a. The change in magnetic anisotropy of Ni as a function of the structural strain is within the error margins. DOI: 10.1103/PhysRevB.87.014428