Sm(Co0.9Cu0.1)5 single-layer thin films and Sm(Co0.9Cu0.1)5/Fe2Co exchange coupled bilayer films with c-axis in the plane (IP) and out of the plane (OOP) orientations were prepared on MgO and Al2O3 single crystalline substrates by magnetron sputtering. Clear relationship between the grain morphology and coercivity was observed for the Sm(Co0.9Cu0.1)5 single-layer films. We found the thermal stability of coercivity is largely influenced by the c-axis orientation because the c-axis IP geometry lowers magnetostatic effect that plays an increasing role at elevated temperature. In Sm(Co0.9Cu0.1)5/Fe2Co bilayer films with the two c-axis geometries, the coercivity show larger dependence on the thickness of the Fe2Co layer for the c-axis IP geometry due to the energetically unfavorable magnetostatic coupling between hard/soft-magnetic layers, which is supported by micromagnetic simulations.
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