Magnetic and structural properties of PrCo3-xSix compounds

We have systematically investigated the magnetic properties of the rare-ear th compounds PrCo8Si and PrCo3-xSix, the crystal structures of which are he xagonal CeNi3-type and rhombohedral Be3Nb-type, respectively. Sharp cusps w ere observed in the real and imaginary parts of the ac susceptibility at te mperatures between 282 (x=0.08) and 209 K (x=0.23). Also observed were bifu rcations of the zero-field-cooled and field-cooled magnetization curves at the same temperatures, showing that the magnetization was irreversible belo w these temperatures. The effect of Si substitution for Co in this system i s to decrease the average ferromagnetic exchange interaction, thus decreasi ng the Curie temperature, without introducing significant random magnetism effects due to exchange fluctuations or random magnetic anisotropy. (C) 199 8 American Institute of Physics. [S0021-8979(98)46211-X].