Effect of Ga substitution on the magnetocrystalline anisotropy of arc-melted Sm2Co17-xGax (x=5,6) compounds

The effect of Ga substitution on the magnetocrystalline anisotropy of Sm2Co 17-xGax (x = 5,6) compounds has been investigated by means of x-ray diffrac tion (XRD) and magnetic measurements. XRD patterns show that the samples st udied here crystallize in the rhombohedral Th2Zn17-type structure. The Curi e temperature for Sm2Co12Ga5 and Sm2Co11Ga6 is 367 and 166 K, respectively, according to thermal-magnetic curves. XRD measurement on the magnetically aligned sample shows that the room temperature easy magnetization direction of Sm2Co12Ga5 compound corresponds to the c axis. The spin-reorientation t ransition is observed at 32 K for Sm2Co11Ga6. The anisotropy constants K-1 and K-2 of Sm2Co17-xGax (x = 5,6) were derived by fitting the magnetization recoil curve measured between 5 K and their Curie temperature. An anomalou s jump in magnetization is found in the magnetization curve of Sm2Co12Ga5 c ompound. In order to investigate the temperature dependence of the critical field H-crit in which the jumps of magnetization occur, hysteresis loops w ere measured in a field range of -90-90 kOe between 5 and 150 K. The critic al field is found to shift rapidly to lower value with increasing temperatu re. (C) 2001 American Institute of Physics.