Large magnetostrictive susceptibility in Tb-FeCo/FeCo multilayers

[Tb(Fe0.55Co0.45)(1.5)/Fe](n) and [Tb(Fe0.55Co0.45)(1.5)/(Fe0.5Co0.5](n) multilayers were fabricated by rf-magnetron sputtering from composite targets. Magnetostriction was measured using an optical deflectometer. The as-deposited films showed a soft magnetic and magnetostrictive character, with a coercive field mu H-0(c)=5 mT and a parallel magnetostrictive susceptibility chi (lambda parallel to)=d lambda (parallel to)/d(mu H-0)=1.4x10(-2) T-1. This magnetostrictive softness was strongly improved by heat treatments: the magnetostrictive susceptibility attains the huge value of 5x10(-2) T-1 in applied field of 6 mT. The low-field dependence of the magnetostrictive susceptibility and their technical characters are described in detail. (C) 2001 American Institute of Physics.