Microstructure dependence of magnetization mechanisms in Co-Fe thick films

Abstract

Magnetization reversal mechanisms in electrodeposited Co100−xFex (x = 0; 20; 30; 50) films are investigated by measuring the angular dependence of coercivity and relative remanence at room temperature. Deposition is performed onto Cu substrates using the pulse-reverse plating technique under nearly zero-field (B0 condition) and under a constant magnetic field of 100 mT (B100 condition), which is applied perpendicular to the Cu substrate, providing different microstructural scenarios according to composition, grain shape and size, film thickness and crystallographic texture. Iron-containing films deposited under the magnetic field are thinner, low textured and exhibit a smaller grain size scale. Films are soft ferromagnetic, with a nearly in-plane easy axis. The B100 condition and the iron content promote larger coercivities, independently of composition, the film thickness and the relative orientation between the film plane and the applied field. The angular dependence of coercivity reaches a maximum near 75–80° and a minimum near 90°, the hard axis direction. This maximum arises from a transition from a magnetization switching mechanism controlled by domain wall depinning to another one, controlled by inverse domain nucleation inside the grains. This transition is mainly controlled by grain size; it disappears when localized nucleation of inverse domains becomes less competitive (more difficult) by extensive exchange coupling of small grains.