The structure and magnetic properties of sputtered FePtM (M = Ta, Cr) thin films

FePt thin films with various Ta and Cr concentrations ranging from 3.6 to 11.6 at.% were prepared by rf magnetron sputtering and characterized for structure and magnetic properties. The films were post-annealed in vacuum at 600degreesC for 1 h, followed by quenching in argon to room temperature. The additive elements are found to be beneficial for refining the grain structures of FePt alloy films. All the concentrations of Cr used in the present study (5.3-9.6 at.%) and a high Ta content (11.3 at.%) are observed to effectively inhibit the formation of ordered phase during annealing. The addition of Ta and Cr decreases the coercivity in FePt thin films and increases the saturation magnetization except for a doping of 9.6 at.% Cr. The high energy product of 32.1 MG Oe is obtained for 7.1 at.% Cr-doped film as a consequence of the grain refinement and retention of disordered phase. The optimum doping concentrations were 7.9 and 7.1 at.%, respectively, for Ta- and Cr-doped FePt alloy thin films. The addition of non-magnetic atoms in FePt thin films thus enhances the magnetic properties and leads to noise reduction for the potential high density recording media application.