STRAIN, INTERDIFFUSION, MAGNETISM AND MAGNETIC-ANISOTROPY IN CU NI/CU(001) SANDWICHES/

The effects of interface, strain and interdiffusion on magnetic moment s and magnetocrystalline anisotropy in Cu/Ni/Cu(0 0 1) trilayers have been studied by first-principles spin-polarized relativistic band-stru cture calculations. Ideal Cu/Ni-n/Cu(0 0 1) trilayers are modelled by NinCu5(0 0 1) superlattices (n = 1, 3, 5) whilst Ni/Cu interdiffusion is simulated by (NiCu)(2)Ni-n(NiCu)(2)Cu-3(0 0 1) superlattices (n = 3 , 5, 7) containing two Ni/Cu mixed monolayers (ML) at each Ni/Cu inter face. The main results include that ideal Cu/Ni-n/Cu(0 0 1) trilayers (n greater than or equal to 5) exhibit magnetoelastic properties very similar to that of bulk Ni and the flat Ni/Cu interface anisotropy is in-plane but small (-0.01 meV/surface atom), that the perpendicular ma gnetocrystalline anisotropy (PMA) of ideal Cu/Ni-n/Cu(0 0 1) trilayers (n greater than or equal to 5) predominantly comes from the magnetoel astic anisotropy due to Ni/Cu lattice mismatch strain, and that one si ngle Ni monolayer embedded in Cu is nonmagnetic and so are the Ni atom s in the Ni/Cu mixed layers two Mt away from the Ni slab. The first sp in-orientation transition from an in-plane orientation to the perpendi cular magnetization in the ideal Cu/Ni/Cu(0 0 1) trilayers is predicte d to occur at Ni film thickness of about 3 ML. Introducing (-0.29 meV/ surface atom), thus postponing the first spin-orientation transition t ill 6 ML. Ni film thickness of the second spin-orientation transition from the perpendicular direction back to an in-plane magnetization is estimated to be around 40-60 ML. The calculated bulk Ni magnetostricti on coefficient is in reasonable agreement with experiments. The calcul ated PMA is related to the Ni orbital moment anisotropy and also to th e Ni d-orbital-decomposed density of states near the Fermi level. (C) 1997 Elsevier Science B.V. All rights reserved.