Co magnetism and related phenomena in the Er(Co1-xSix)2 compounds

Results of magnetic, transport and dilatometric studies of the Er(Co1-xSi)(2) compounds (for x less than or equal to 0.15) in ambient and elevated pressures are presented. The Si substitution for Co yields a dramatic increase of T-C although the room-temperature lattice volume does not change. The first-order magnetic phase transition at T-C observed in ErCo2 persists for x less than or equal to 0.075. The large resistivity drop observed just below T-C and the negative magnetoresistance accompanying the field-induced metamagnetic transition above T-C are attributed to Fermi surface reconstruction and to quenching of Co 3d spin fluctuations due to Co moment formation. Formation of the Co magnetic moment is reflected also in a pronounced lattice expansion. The resistivity, magnetoresistance and thermal expansion anomalies are progressively reduced with increasing x (and also with external pressure), which can be conceived with a progressively reduced Co moment. Application of external hydrostatic pressure causes reduction of T-C at a rate partial derivative ln T-C/partial derivative p similar to -30 Mbar(-1) in all the studied compounds. (C) 1998 Elsevier Science B.V. All rights reserved.