Structure and magnetic properties of Fe1−<i>x</i>Ni<i>x</i>/Cu Invar superlattices

Abstract

We have prepared by sputtering techniques a series of fcc [Fe1−xNix/Cu]×10 superlattices with sublayer thicknesses of 3 nm and with Ni concentrations x ranging from 0.26 to 0.54. The use of MgO single-crystal substrates and Cu sublayers in the superlattice growth ensures a well-defined fcc crystal structure in the Fe–Ni sublayers with a Ni concentration as low as 26 at. % and down to liquid helium temperatures. The magnetization of the Fe–Ni sublayers in the superlattices starts to deviate from the well-known Slater–Pauling curve at 40 at. % Ni, and continues to drop until the fcc–bcc transition is completed. A strong dependence of the magnetization on temperature was also observed for the Fe–Ni sublayers in the Invar range, consistent with the behavior of bulk Fe–Ni Invar alloys.