Origin of the magnetic anisotropy in ferromagnetic layers deposited at oblique incidence

Ferromagnetic films evaporated at oblique incidence show invariably an uniaxial in-plane magnetic anisotropy component with easy axis perpendicular to the incidence plane. Scanning Tunneling Microscopy (STM) images reveal that oblique deposition results in rough films with highly anisotropic correlation functions of the surface profile. We show that simple shape anisotropy calculations using high-quality STM roughness data as input reproduce the measured anisotropies remarkably well and unambiguously relate them to the long-ranged dipolar interactions.