Magnetic Properties and Microstructure of Bias-Sputtered CoZr Films

The effects of a negative bias voltage during film preparation on both the magnetic properties and microstructure of Co₉₂Zr₈ (at%) films deposited by rf magnetron sputtering have been investigated. A low coercive force H_c and high permeability μ are obtained when negative bias voltages lower than -75 V are applied. Values of the magnetostriction constant λ_s for bias-sputtered films are smaller than those for unbiased films. The μ value for bias- sputtered films after 1000 hours of heat treatment at 80°C decreases to approximately 80% of its initial value, while a decrease of about 40% is observed for unbiased films. The decrease in λ_s values and the improvement in stability of the permeability can be explained in terms of the structural difference between films sputtered with and without a bias voltage applied. It is concluded that bias-sputtered films with a negative bias voltage below -75 V are excellent candidates for use as thin film head pole pieces.