Effect of Pr on the Structure and Magnetic Properties of CoPt Alloys

The effects of Pr on the microstructure and magnetic properties of PrxCo50-xPt50 alloys (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were investigated. The XRD results indicate that all the alloys homogenized at 1000 degrees C contain only a single Al (fcc) phase, while the alloys annealed at 675-750 degrees C consist of a hard-magnetic face-centered-tetragonal (fct) phase and a magnetically soft fcc phase. The (111) reflection belonging to the fct phase shifts to a higher angle and the c/a ratio increases as the Pr content increases, which leads to a decrease in the degree of ordering, S. Maximum values for the coercivity H-c and the remanence ratio m(r) are achieved in Pr0.4Co49.6Pt50 alloys annealed at 675 degrees C for 60 min. For the series of PrxCo50-xPt50 alloys annealed at 675 degrees C for 60 min, H-c decreases monotonically with increasing of Pr concentration, but m(r) is first enhanced and then weakened, showing a maximum value of 0.82 at x = 0.4 to 0.6.