Magnetic Properties and Magnetization Reversal of Sm–Co(3x nm)/Co(x nm) Multilayered Films

Abstract

[Sm–Co (3x nm) /Co (x nm)]10 (x = 10, 7, 4) multilayered films have been prepared by magnetron rf-sputtering. It is found that the thickness of both hard and soft layers has important effects on phase transformation and magnetic interaction of films. With a fixed ratio of hard- to soft-layer thickness, decreasing simultaneously the thickness of these layers results in increasing coercivity. The effects of the external magnetic field during annealing depend on the Co-layer thickness (x value), mainly because of the formation of different main phases for different thickness of Co layer. For the films with x = 10 and 7, the main phase is Sm2Co17 after annealed. Applying a magnetic field during annealing promotes the crystallization of films, and therefore, it increases the coercivity of the films with x = 10 and 7. Magnetic interaction has been investigated by measuring δm and remanence magnetization. All the films show that although the exchange coupling favorable for magnetization is significant, the increase of the coercivity mainly originates from improving the pinning effects. Temperature dependence of the coercivity supports that the pinning of domain-walls constitutes a control mechanism of the coercivity. This behavior can be well understood in terms of the Gaunt’s approach of the coercivity.