Magnetism and Magnetoresistance in Fe/Cu Granular Films Produced by Sputter Deposition and Subsequent Annealing

Abstract

Magnetic properties and magnetoresistance (MR) have been studied in homogeneous and granular Fe_xCu_100-x films produced by sputter (SP)-deposition and subsequent annealing. Concentration dependence of the MR ratio shows a maximum at x=20 in the as-SP-deposited films. On the other hand, it shows a monotonic change (no maximum) after annealed at 673, K for 30, min. Such an MR variation by annealing is ascribed to the magnetic transition of Fe clusters in Cu matrices. Mössbauer spectra and thermomagnetic curves observed at low temperatures indicate that the as-SP-deposited Fe_xCu_100-x alloy films are f.c.c. for x<35 being spin-glass, while those ones annealed at 673, K for 30, min are f.c.c. and b.c.c. mixture, being a spin-glass and ferromagnetic complex for x=11 and an antiferromagnetic and ferromagnetic one for x=20.