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

Microstructural features and magnetic behavior of epitaxially grown SmCo thin films with very high in-plane anisotropy are presented. Transmission electron microscopy was used to characterize the microstructure while magnetic measurements were performed using dc and SQUID magnetometers. Two substrate orientations were studied, i.e., MgO(100)/Cr(100)/SmCo(112¯0) and MgO(110)/Cr(211)/smCo(11¯00). In the former, the SmCo(112¯0) film shows a bicrystalline microstructure, whereas in the latter, a uniaxial one is observed. Both microstructures consist of grains with a mixture of SmCo₃, Sm ₂Co₇ and SmCo₅ polytypoids. A deviation from the c-axes was observed in the in-plane anisotropy of the SmCo(112¯0) thin film. A strong exchange interaction between the grains would, in principle, explain the observed deviation, On the other hand, both SmCo(112¯0) and (11¯00) 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