Band metamagnetism and related phenomena in Er(Co1-xSix)(2)

We report on magnetic, transport, and cohesive properties of Er(Co1-xSix)(2) compounds in varying external conditions (T,H,B). The localized Er 4f magnetic moments in ErCo2 order ferromagnetically below T-C=33 K. The Co 3d band states form no moment above T-C, but below Te the majority and minority 3d sub-bands split due to strong 4f-3d exchange interaction. Consequently, Co moments of similar to 1 mu(B) appear coupled antiparallel to the Er moments. This is accompanied by a similar to 50% resistivity drop and an abrupt lattice expansion. The sharp magnetization, resistivity, and volume anomalies in the critical temperature region indicate a first order magnetic phase transition. Detailed comparative studies reveal that the onset of Co magnetizm appears at T-0 similar to(T-C-1) K, Si substitution for Co enhances both, T-C (up to 66 K for x=0.1) and Delta T=T-C-T-0, but the lattice parameter remains unchanged. In opposite, both the magnetovolume and resistivity anomaly at To become reduced. Pressure effect on Tc(To) is large and negative, partial derivative ln T-C/partial derivative p similar to-28 Mbar(-1) for all x less than or equal to 0.1. Also the resistivity drop at T-0 and the magnetovolume effect (omega(s)=3 Delta L/L=4.2x10(-3) in ErCo2) below T-0 become reduced with increasing pressure. The latter is reflecting reduction of the Co moment gained below T-0. (C) 1997 American Institute of Physics.