Exchange coupling and magnetic properties of Sm–Co/Fe65Co35 multi-layered films

A detailed analysis of exchange coupling are made for sputtered [Sm-Co(21 nm)/Fe65Co35 or Co(x nm)](10) (x = 5 or 7) multi-layered films. After annealing, a main phase obtained within the films is Sm2Co17. Transmission electron microscopic observation illustrates that the film exhibits a nano-particle structure and no multi-layer structure forms after annealing. deltam measurements and remanence magnetization curves with applying field show that the increase in coercivity might be due to improving pinning effectiveness by decreasing Fe-Co layer thickness or changing from Fe-Co to Co layer. The recoil curves are analysed in detail for [Sm-Co(21 nm)/Fe65Co35(x nm)](10) multi-layered films, which shows that the recoil susceptibility of the [Sm-Co(21 nm)/Fe65Co35(5 nm)](10) film is lower and changes slowly. These results can be understood in terms of a pinning-type mechanism of coercivity and the exchange coupling between grains of hard and soft magnetic phases.