Influence of deposition conditions on magnetic properties of CoCr thin films

Abstract

CoCr thin films were sputtered with varying values of target bias, forward power, sputtering rate and argon pressure. Cr content, saturation moment, coercivity, squareness, perpendicular anisotropy Ku, and net anisotropy (Ku−2πM2s) were measured. It was found that perpendicular or in-plane squareness measurements with a VSM were not a useful indicator of perpendicular anisotropy (as determined by torque magnetometry). Net perpendicular anisotropy (Ku−2πM2s) was found to increase with deposition rate. Most films showed positive net perpendicular anisotropy, with no substrate heating necessary other than that provided by the sputtering process. Saturation moment was found to decrease with increasing target bias, a variation not explainable by differences in average Cr content. Perpendicular anisotropy and perpendicular coercivity decreased with increasing target bias also. These results suggest a common microstructural mechanism affecting all three properties. Alternate explanations involving oxidation, Cr distribution (short-range order, or segregation of Cr-rich phases), and argon incorporation could explain these results, but will require further experiments to establish.