Diffusion-induced stress and magnetic anisotropy

Crystalline-Ni/amorphous-Ni50Zr50 and crystalline-Co/amorphous-Co50Zr50 multilayers were produced by de planar magnetron sputtering. Magnetic hysteresis loops were measured using a vibrating sample magnetometer. Multilayers were characterised in the as-deposited state, and after successive isothermal anneals. For the c-Ni/a-NiZr multilayers, the change in the hysteresis loops on annealing is consistent with a reversal in anisotropy brought about by a diffusion-induced tensile stress in the magnetic Ni layers. The c-Co/a-CoZr films show no such changes in hysteresis on annealing. The divergence in the behaviour of the two different types of film is attributed to the difference in the magnetic properties of Ni and Co.