Magnetoelastic properties of very thin Co-alloy films

The magnetoelastic properties of thin longitudinal Co-alloy films were investigated by measuring the changes in the hysteresis loop during and after the application of a mechanical strain. Co, Co₉₀Pt ₁₀, Co₈₈Cr₁₂, and Co₇₈Pt₁₀Cr₁₂ thin films, ranging in thickness and from 250 to 3000 Å, were deposited on Mylar substrates and subjected to bending strains in the 10^-3 range. For all samples the coercivity, coercive squareness, and remanent squareness decreased along the tensile axis, consistent with a negative magnetostriction constant. The magnetoelastic effects were found to scale approximately as H_c^-1. The consequences of these observations for magnetic recording-in particular, stress-induced signal loss and transition broadening-are discussed. It is pointed out that temporary application of stress on a recorded medium can have a twofold effect: a partial demagnetization of the recorded cells and a broadening of the transitions. It is estimated that, for the type of alloys investigated, both these effects should be on the order of a few percent per 1% strain for coercivities of 1000 Oe