Approach to magnetic saturation in sputtered amorphous films: Effects of structural defects, microscopic anisotropy, and surface roughness

Abstract

We have studied the approach to magnetic saturation in sputtered amorphous films by superconducting quantum interference device (SQUID) magnetometry. We observe a 1H law for the deviation M from complete saturation. The effect is an order of magnitude smaller than earlier results on liquid-quenched ribbons. We show that the effect cannot be due to surface roughness or macroscopic anisotropy. We attribute the behavior to magnetoelastic anisotropy arising from linear defects of a quasidislocation or cylindrical-volume-defect type, running perpendicular to the film plane. We deduce a defect density order 1015 m-2 and effective Burgers vector of order 3 in an as-grown Fe-Ni-B film. We also show how this method can be used to determine the microscopic spatially uncorrelated anisotropy, and we set an upper limit of order 106 J/m2 in the Fe-Ni-B film. © 1984 The American Physical Society.