Magnetization reversal in CoFeHfO films

Magnetization reversals of a thick CoFeHfO film (800 mn), and a thin CoFeHfO (10 nm) film overcoated with CrSi (10 nm) have been studied by magnetic force microscopy (MFM) with in situ applied field capability. The CoFeHfO layers were deposited by RF sputtering and annealed in a magnetic field to induce an in-plane uniaxial anisotropy. For easy-axis applied fields both samples showed significant switching of MFM image contrast for fields approximately equal to the coercivity. This is consistent with the high easy-axis coercive squareness of the films. For hard-axis applied fields the thin CoFeHfO film displayed a distinctive reversal process: a ripple-like domain pattern formed and rotated gradually as the reversed field was increased. The image contrast increased, reached a maximum when the ripple-like features aligned perpendicular to the field and then diminished as the sample approached saturation. The observed magnetization reversal processes appear to be consistent with the formation of magnetization ripples which rotate toward the hard-axis applied field.