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

Magnetization and Mossbauer spectroscopic measurements are reported on five alloys in the series (Fe1-xCox)(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 Fe2P-like hexagonal one to Co2P-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. (C) 2001 Elsevier Science B.V. All rights reserved.