Structure evolution, magnetic domain structures and magnetic properties of CoPt–C nanocomposite films

Abstract

CoPt–C nanocomposite thin films with various carbon concentrations were prepared by a pulsed filtered vacuum arc deposition technique. Annealing was performed in vacuum for 1 h at various temperatures. The structure evolution and magnetic properties of the films were characterized by non-Rutherford backscattering spectrometry, X-ray diffraction, magnetic force microscopy and vibrating sample magnetometer. The as-deposited samples are magnetic soft with face-central-cubic phase CoPt nanocrystals encapsulated in carbon matrix. After annealing at a sufficiently high temperature, depending on the carbon composition, the CoPt nanocrystals transform to a face-centered-tetragonal phase. For the film with a particular composition of (Co 0.44Pt 0.56) 0.55C 0.45, the coercivity is observed to increase with increasing annealing temperature, up to a value of 7 kOe at an annealing temperature of 750°C, and the grain size increases from 9 to 20 nm.