Interplay of magnetic anisotropies on the magnetostrictive behavior of Fe–Co thin films

This paper reports the structure, microstructure, domain imaging and magnetostrictive properties of Fe₅₀Co₅₀ thin grown on Si < 100 > substrates with different thicknesses namely 40, 80, 100 and 120 nm. Structural studies revealed that the films are crystalline in nature with bcc type structure. Magnetization studies exhibited predominant in-plane magnetic anisotropy for all the films. In addition to this films grown with higher thicknesses also showed co-existence of out-of-plane magnetic anisotropy along with in-plane magnetic components. Angle dependent hysteresis measurements indicated presence of weak uni-axial magnetic anisotropy along the plane for all the films. Longitudinal magneto-optic Kerr microscopy studies revealed nucleation of reverse domains for the film grown with low thickness. Wide band domains with few zig–zag branched features have been observed for the films grown with higher thicknesses. Magnetic force microscopy investigations along the out-of-plane direction showed increase in magnetic phase contrast with increase in film thicknesses. Magnetostriction derived from the deflection measurements are found to decrease with increase in film thicknesses. Presence of competing anisotropies has been found to be prominent reason for the decrease in the magnetostriction with increase in film thickness.