Magnetic and structural studies in Co-Al thin films

Abstract
Thin films of Co100−xAlx with 15<x<50 were prepared by evaporation. The as-deposited films had the hexagonal Co structure for x30. After a heat treatment at 650 °C the films with x<25 changed microstructure to a fine mixture of hcp Co and an ordered fcc structure which may be interpreted as Co3Al. Films with 25≤x≤50 were transformed to ordered fcc Co3Al and bcc CoAl structures after the heat treatment. The magnetization of the films was greater than for bulk alloys with the same composition and it decreased when the films were annealed at 650 °C. The finely distributed two-phase microstructure is probably responsible for the observed coercivity (50–150 Oe).