Hard magnetic two-phase Co-Cu thin films

The magnetic properties of sputtered films of 25 Co-75 Cu and 50 Co-50 Cu before and after annealing were investigated. In the as-sputtered state the films exhibit the structure of a metastable fcc solid solution. Annealing at 500 to 700°C causes decomposition into two phases, Cu and fcc 89 Co-11 Cu. The decomposition supposedly occurs by heterogeneous nucleation at the grain boundaries, and growth by grain boundary diffusion. The 89 Co-11 Cu phase exists in the form of small particles with magnetic single domain behavior. The films have coercivities up to 280 Oe. Squareness ratios between 0.7 and 0.9 were found. No strain sensitivity of the magnetic properties could be detected. This material is regarded to be suitable for magnetic recording.