Magnetic behaviour of alloys in the series (Fe1−xCox)2P

Abstract Magnetization and Mossbauer spectroscopic measurements are reported on five alloys in the series (Fe 1− x Co x ) 2 P (corresponding to x =0.03, 0.10, 0.30, 0.50 and 0.70). All the five alloys are ferromagnetically ordered. With increasing cobalt, the Curie temperature initially increases becoming maximum for x =0.30 at 480 K and then drops. In going from x =0.10 to 0.30, when the crystalline symmetry changes from Fe 2 P-like hexagonal one to Co 2 P-like orthorhombic one, the magnetic moment on the pyramidal metallic site tilts off the V zz -axis. In all the compositions, substitution of cobalt reduces the internal magnetic field at the tetrahedral site whereas that at the pyramidal site shows little change. The system with x =0.03 exhibits temporal relaxation of magnetization over a long period of time. Mossbauer spectra of this alloy exhibit a reduction in linewidth with increasing temperature from 80 to 125 to 160 K. These observations are indicative of the existence of magnetic clusters.