Effect of deposition parameters on rf sputtered CoZr and CoZrRe thin films for magnetic recording heads

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Abstract
It has been shown by Tago, Nishimura, and Yanagisawa [IEEE Trans. Magn. M A G ‐ 2 1, 2032 (1985)] that addition of small amounts of Re to CoZr produces material with zero magnetostriction. We have prepared CoZr and CoZrRe amorphous films by rf sputtering, producing alloys with soft magnetic characteristics suitable for use in thin‐film recording heads. The dependence of coercivity, anisotropy field, and saturation magnetization on sputtering conditions and film composition has been characterized. Co93Zr7 films have been fabricated with 4πMs of 15 kG and Hc less than 0.4 Oe in the as‐sputtered state. Similar results were obtained with Co92Zr6Re2 films. The films which exhibited the best soft magnetic properties were deposited at low target bias, 5‐mTorr argon pressure, and zero substrate bias. Below 1500‐V target bias, low anisotropy field was accompanied by a dispersion factor of up to 4° in CoZr and up to 9.5° in CoZrRe films. Coercivity and anisotropy field both increased with increasing target bias, whereas film dispersion decreased. These effects were accompanied by a decrease in Zr content in both CoZr and CoZrRe films of up to 5 at. % across the range of target biases. It is believed that, at bias greater than 2500 V, substrate heating was also significant in determining film characteristics. Increasing argon pressure increased the coercivity and anisotropy field, which is in agreement with previously published results for CoZr. Applying bias to the substrate also increased the coercivity and anisotropy field, producing films with undesirable magnetic properties. Trends and limitations of the deposition technique are analyzed and discussed.