Effect of ion beam energy on magnetic properties of CoCrPt and CoPt thin films

Abstract

The magnetic properties of Cr/CoPt and Cr/CoCrPt thin films prepared by ion beam deposition with Xe ions (0.6–1.5 kV) have been investigated. The effect of ion beam energy on the structural and magnetic properties has been studied. A strong dependence of in-plane coercivity on the beam energy was observed and the coercivity increased with beam energy for both CoPt and CoCrPt thin films. With increasing beam energy from 600 to 1500 eV, the coercivity for CoPt thin films increased from 1700 to 2100 Oe. In addition, CoPt thin films have a greater advantage over CoCrPt thin films. A 40% increase in coercivity for CoPt thin films was obtained at the same remanent magnetization-thickness (Mrt) product as compared to CoCrPt. A minimum thickness of 20 Å for the Cr underlayer and 600 eV beam energy were required for constant coercivity and Mrt. X-ray diffraction studies indicated that CoPt(101̄0) texture and in-plane hcp c-axis orientation were enhanced with increased beam energy. The increase of coercivity with beam energy is attributed to an increase in the peak intensity ratio (101̄0)/(0002). The decrease of grain size for CoPt(101̄0) texture with beam energy was attributed to contribute to improvement in coercivity. Compositional analysis using inductively coupled plasma indicated that the Pt content in CoPt thin films increased with beam energy. The increase of Pt content in the thin films accompanied by an increase in the d spacing (lattice constant) improved in-plane coercivity. From magnetic force microscopy studies, lower inter-granular exchange coupling was observed at higher beam energy.