Investigation of obliquely evaporated nanocolumnar cobalt films

Cobalt films 100 nm thick were thermally evaporated on NaCl crystals at an incidence angle of 45° in a vacuum of approximately 10−5 mbar. The morphological structure of the films consisted of closely packed nanocrystalline grains, typically a few tens of nanometers in size. The alignment of nanocolumnar grains in the direction perpendicular to the incidence plane was observed. The magnetic structure was composed of domains running predominantly in the direction parallel to the incidence plane. The domains were about 1 μm wide and substantially magnetized in the plane of the film. Because of the stripe and regular character of the magnetic domains, exchange coupling between the grains is found to be strong and homogeneous. The films were mainly composed of the hexagonal close-packed (HCP) phase of cobalt. The alignment of magnetic domains in the direction parallel to the incidence plane means that the crystallographic contribution to the magnetic anisotropy is dominant over the shape anisotropy.