Magnetostriction of free layer in top-type and bottom-type spin-valve films

We investigated magnetostriction of a free layer in top-type and bottom-typ e spin valves, The magnetostriction of the free layer in the top-type spin valve increased as the thickness of free layer decreased, which can be attr ibuted to the increase in the surface magnetic anisotropy, However, the mag netostriction of the free layer in the bottom-type spin valve exibited no s ignificant change with decreasing in the thickness of free layer, and was s maller than that of in the top-type spin valve. This difference may come fr om the degree of intermixing at the interface of the free layer, We confirm ed by X-ray Photoelectron Spectroscopy that intermixing between the spacer and free layer, Cu and CoFeB respectively, can he quite different for the t op-type and the bottom-type spin valves, and that the magnetostriction can be influenced by the degree of intermixing. The magnetostriction tends to b e small value when intermixing is significant, as we found in the bottom-ty pe spin valve.