Magnetic properties and coercivity mechanism of precipitation-hardened Pr1.0-xGdxCo5.7CuTi0.3 magnets

Pr1.0-x,GdxCo5.7CuTi0.3 (X = 0.0-0.5) samples have been prepared by arc melting and precipitation hardening. X-ray diffraction and transmission electron microscopy reveal that their microstructures consist of a rhombohedral 2: 17 matrix phase surrounded by a hexagonal 1 : 5 cell boundary phase. Gd addition leads to an increase in the Curie temperatures of both the 1 : 5 and 2: 17 phases. The temperature coefficient of saturation magnetization (77 = d J(S)/dT) increases with increasing x and a nearly zero eta is obtained in the magnet with x = 0.5. Positive temperature coefficients of coercivity H-c and energy product (BH)(max) have been observed in all samples. Thus, Hc of about 0.7 T and (BH)(max) of about 3.0 MG Oe are obtained in the Gd-substituted sample at high temperatures. The magnetization reversal of the Pr-Co based precipitation-hardened magnets is dominated by domain-wall pinning in the whole temperature range.