Effect of Film Thickness on Morphology and Magnetic Properties of CoPt Thin Films

The separated CoPt nano-size islands were fabricated on amorphous glass substrates in this work. The microstructures and magnetic properties of CoPt thin films with thicknesses between 1 and 20 nm after annealing at 700 degrees C for 30 minutes were investigated. The morphology of CoPt thin film would change from a well-distributed and discontinuous nano-size CoPt islands into a continuous film as increasing the film thickness from 1 to 20 nm. The formation mechanism of the CoPt islands may be due to the surface energy difference between the glass substrate and CoPt alloy. Each CoPt island was composed of multi-CoPt particles. This discontinuous nano-island CoPt recording film may increase the recording density and enhance the signal to noise ratio while comparing with the continuous films. The 7.5 nm-thick CoPt film revealed an out-of-plane coercivity (H(c perpendicular to)) of 12.0 kOe and had separated islands after annealing at 700 degrees C for 30 minutes. This nano-size CoPt thin film may be a good candidate for ultra-high density magnetic recording media due to its discontinuous islanded nanostructure and good magnetic properties.