Microstructure and Magnetic Properties of Sputter-Deposited Ho–Co Alloy Thin Films with Perpendicular Magnetic Anisotropy

The structures of Ho19Co81 thin films fabricated by r.f. sputtering in Ar atmosphere are discussed. Electron microscopic observation shows that a columnar structure is developed along the direction of the film thickness. Each column is largely amorphous but contains locally-microcrystalline regions 30–50 A in size. A high-resolution photograph of the lattice image indicates that these microcrystalline regions very likely consist of HoCo5 in a short range, and that the hexagonal c-axis is nearly directed along the thickness direction. It is suggested that the presence of such microcrystalline regions may need to be taken into account in discussing the origin of the observed perpendicular magnetic anisotropy in rare-earth transition metal amorphous films.