MAGNETISM AND RELATED PHENOMENA IN RE(CO1-XSIX)(2) COMPOUNDS

We report on crystal structure, magnetic, transport and dilatometric s tudies of the pseudobinary compounds RE(Co1-xSix)(2) with RE = Nd, Ho and Er for x less than or equal to 0.15. The lattice volume of the Ho and Er-based compounds is almost composition invariable, whereas in Nd (Co1-xSix)(2) for x between 0 and 0.15 it increases by similar to 7%. Already small Si substitutions for Co (x less than or equal to 0.075) induce a dramatic increase of T-C both in the Ho and Er compounds with out apparent loss of the first order character of the magnetic phase t ransition, whereas opposite changes of T-C are observed in Nd analogue s. These results, together with variations of resistivity and magnetov olume anomalies at T-C and of the Co magnetic moment observed in all t hree systems is discussed in terms of expected changes of electronic s tructure and their influence on the hierarchy of exchange interactions and formation of the Co moment in this class of materials. (C) 1997 E lsevier Science S.A.