The influence of substituting Si for Co on the magnetic properties of PrCo5

The crystal structure and magnetic properties of the PrCo4.5Si0.5 compound have been investigated. PrCo4.5Si0.5 is found to be ferromagnetic in the whole ordered region with a CaCu5 crystal structure type. The Si for Co substitution induces an important reduction of the Curie temperature (TC), TC that reaches 645(2)K. At 4K, the saturation magnetization is 8.0μB/f.u. Powder neutron diffraction data show that the Co atoms from non-equivalent atomic sites (2c, 3g) are exhibiting a similar magnetic behavior. The magnitude of the atomic magnetic moments diminishes with increasing temperature. At low temperatures, the magnetic moments are tilted away from the c-axis. As the temperature increases the magnetic moments become parallel to it. This spin reorientation is observed between 50 and 90K in PrCo4.5Si0.5. At 300K the atomic magnetic moments are μCo2c=1.19(3)μB, μCo3g=0.98(3)μB, μPr=0.59(8)μB being aligned along the c-axis. The Si atoms are localized exclusively at the 3g site, thus favoring an enhancement of the uniaxial anisotropy