Large magnetostrictive susceptibility in Tb-FeCo/FeCo multilayers
[Tb(Fe0.55Co0.45)1.5/Fe]n and [Tb(Fe0.55Co0.45)1.5/(Fe0.5Co 0.5]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 μ0Hc=5 mT and a parallel magnetostrictive susceptibility χλ∥=dλpar;/d(μ0H) =1.4×10-2 T-1. This magnetostrictive softness was strongly improved by heat treatments: the magnetostrictive susceptibility attains the huge value of 5×10-2 T-1 in applied field of 6 mT. The low-field dependence of the magnetostrictive susceptibility and their technical characters are described in detail. © 2001 American Institute of Physics.