Parallel Oblique-Incidence Anisotropy in NiFe Films

Abstract

Magnetic films exhibiting an easy axis normal to the incidence plane (perpendicular anisotropy) when deposited at oblique incidence are well known. Anisotropic crystallite chains created by self-shadowing were postulated to explain this effect. One of the physical measurements supporting this model was the observation of optical dichroism. In the present work, an easy axis parallel to the incidence plane (parallel anisotropy) has been found in nonmagnetostrictive films deposited at low (<45°) incidence angles for certain substrate temperatures and film thicknesses. The value of Hk and direction of the easy axis in oblique incidence films was very sensitive to changes in incidence angle, substrate temperature, film thickness, and deposition rate. The magnitude of the magnetic anisotropy Hk was found to be linearly related to the magnitude of the dichroism Δγ by the same constant, dHk/dΔγ = 5.5 × 105 Å·Oe, for oblique incidence films having either parallel or perpendicular anisotropy. This result furnishes strong support for the view that parallel, like perpendicular oblique incidence anisotropy, originates in anisotropic microstructure, e.g., columnar growth. The resultant anisotropy is thus the result of a delicate balance between the crystallite chains and the columns.