Effect of passivation layers on the magnetic properties of SmCo5

We measured the magnetic properties of sputtered SmCo5 films with two different capping layers to assess passivation. Amorphous SiNx and polycrystalline chromium passivation layers were tested. Chromium is an oxygen getter and reported to enhance magnetic anisotropy. SiNx is a good diffusion barrier to oxygen. These two passivation layers have different morphologies when deposited using room temperature sputtering. The magnetic properties of the chromium passivated films were degraded relative to SiNx upon exposure to air. No annealing was performed to minimize high temperature oxidation from adventitious oxygen introduced during deposition. A decrease in the saturation moment and anisotropy was observed upon exposure to air for the SmCo5 layer with chromium passivation. Secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM) measurements were used to analyze the oxygen content.