Strain, interdiffusion, magnetism and magnetic anisotropy in Cu/Ni/Cu (0 0 1) sandwiches
Journal
Journal of Magnetism and Magnetic Materials
Journal Volume
176
Journal Issue
2-3
Pages
97-110
Date Issued
1997
Author(s)
Abstract
The effects of interface, strain and interdiffusion on magnetic moments and magnetocrystalline anisotropy in Cu/Ni/Cu(0 0 1) trilayers have been studied by first-principles spin-polarized relativistic band-structure calculations. Ideal Cu/Nin/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)2Nin(NiCu)2Cu3(0 0 1) superlattices (n = 3, 5, 7) containing two Ni/Cu mixed monolayers (ML) at each Ni/Cu interface. The main results include that ideal Cu/Nin/Cu(0 0 1) trilayers (n ≥ 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 magnetocrystalline anisotropy (PMA) of ideal Cu/Nin/Cu(0 0 1) trilayers (n ≥ 5) predominantly comes from the magnetoelastic anisotropy due to Ni/Cu lattice mismatch strain, and that one single Ni monolayer embedded in Cu is nonmagnetic and so are the Ni atoms in the Ni/Cu mixed layers two ML away from the Ni slab. The first spin-orientation transition from an in-plane orientation to the perpendicular magnetization in the ideal Cu/Ni/Cu(0 0 1) trilayers is predicted to occur at Ni film thickness of about 3 ML. Introducing two Cu/Ni mixed layers at each interface is found to give rise to a large in-plane interface anisotropy (-0.29 meV/surface atom), thus postponing the first spin-orientation transition till 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 magnetostriction coefficient is in reasonable agreement with experiments. The calculated PMA is related to the Ni orbital moment anisotropy and also to the Ni d-orbital-decomposed density of states near the Fermi level. © 1997 Elsevier Science B.V. All rights reserved.
Type
journal article