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

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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.