High coercivity and high hysteresis loop squareness of sputtered Co-Re thin film

Abstract

The coercivity, hysteresis loop squareness, and microstructure of the sputtered Co and Co-rich Co-Re alloy thin films are presented. Correlations between the microstructures and the magnetic properties are established. It was found that the sputtered Co films have a mixture of fcc and hcp phases, making it impossible to obtain sputtered Co films possessing both high Hc and high M-H loop squareness. For Co-Re alloy films however, it was possible to obtain films with a pure hcp phase below substrate temperatures of 300 °C. By controlling the microstructure of the Co-Re films through variation of the sputtering variables, films having Hc’s up to 700 Oe and squareness ratios (Mr/Ms and S*) of more than 80% were obtained. The micromagnetic structures of these Co-Re films were also investigated using Lorentz microscopy and the results are discussed in terms of the microstructure and magnetocrystalline anisotropy of the film.