Evolution of magnetism in Nd(Co1-xSix)(2) and Ho(Co1-xSix)(2)

We report on a comparative study of the effects of Si doping and of externa l pressure on magnetism and related phenomena in Nd(Co1-xSix)(2) and Ho(Co1 -xSix)(2) compounds. The lattice volume in the Ho system is almost composit ion invariable for x up to 0.1, whereas an increase of approximate to 6% is observed in the Nd system. Si substitutions for Co cause a dramatic increa se of T-C in the Ho system for x less than or equal to 0.075 and a gradual reduction of T-C in Nd analogs, whereas the Co moment becomes suppressed fo r x > 0.05 in both cases. Negative pressure effects both on T-C and the Co magnetic moment, although quantitatively different, are found in both syste ms. Expected changes of electronic structure and their influence on the hie rarchy of exchange interactions and formation of the Co moment are discusse d. (C) 1998 American Institute of Physics. [S0021-8979(98)40011-2].