Tailoring of in-plane magnetic anisotropy in polycrystalline cobalt thin films by external stress

Polycrystalline Co films of nominal thickness similar to 180 angstrom were deposited on intentionally curved Si substrates. Tensile and compressive stresses of 100 MPa and 150 MPa were induced in the films by relieving the curvature. It has been found that, within the elastic limit, presence of stress leads to an in-plane magnetic anisotropy in the film and its strength increases with increasing stress. Easy axis of magnetization in the films is found to be parallel/transverse to the compressive/tensile stresses respectively. The origin of magnetic anisotropy in the stressed films is understood in terms of magneto-elastic coupling, where the stress try to align the magnetic moments in order to minimize the magneto-elastic as well as anisotropy energy. Tensile stress is also found to be responsible for the surface smoothening of the films, which is attributed to the movement of the atoms associated with the applied stress. The present work provides a possible way to tailor the magnetic anisotropy and its direction in polycrystalline and amorphous films using external stress. (C) 2016 Elsevier B.V. All rights reserved.