Thickness Dependence of the Magnetostriction in Ta/NiFe and Ta/Ni-X/NiFe Films.

The magnetostriction in thin Ta/NiFe films used in spin-valve films was investigated. The anistropy field decreases and the magnetostriction increases for the thin NiFe layer. The magnetostriction increases linearly with reciprocal NiFe layer thickness. A simple theoretical description, which assumes that a bilayered film consists of layers with different magnetostrictions, explains this relationship between the reciprocal thickness and the magnetostriction. Insertion of an NiPt buffer layer at the Ta/NiFe interface affects the decrease in the magnetostriction and reduces its thickness dependence, and it is also possible in the spin-valve films.