Magnetic anisotropy and its microstructural origin in epitaxially grown smco thin films

Abstract

Microstructural features and magnetic behavior of epitaxially grown SmCo thin films with very high in-plaiie anisotropy are presented. Transmission electron microscopy was used t o characterize the niicrostructure while magnetic measurements were performed using dc and SQUID magnetometers. Two substrate orientations were studied, i.e., MgO(100)/Cr(100)/SmCo(1120) and MgO(110)/Cr(211)/SmCo(1100). In the former, the SmCo(1120) film shows a bicrystalline microstructure, whereas in the latter, a uniaxial one is observed. Both microstructures consist of grains with a mixture of SmCo, , Sm 2Co 7 and SmCo s polytypoids. A deviation from the c-axes was observed in the in-plane anisotropy of the SmCo(1120) thin film. A strong exchange interaction between the grains would, in principle, explain the observed deviation. On the other hand, both SmCo(1120) and (1100) thin films show very high coercivity values with pinning-type characteristics. Possible coercivity mechanisms related to intergranular exchange interactions and local variation in magnetocrystalline anisotropy constants are discussed. © 1998 IEEE.