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,p). The localized Er 4f magnetice moments in ErCo2 order ferromagnetically below Tc=33 K. The Co 3d band states form no moment above Tc, but below Tc the majority and minority 3d sub-bands split due to strong 4f - 3d exchange interaction Consequently, Co moments of ∼1 μB appear coupled antiparallel to the Er moments. This is accompanied by a ∼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 T0∼(TC-1) K. Si substitution for Co enhances both, Tc (up to 66 K for x = 0.1) and ΔT=Tc-T0, but the lattice parameter remains unchanged. In opposite, both the magnetovolume and resistivity anomaly at T0 become reduced. Pressure effect on Tc(T0) is large and negative, ∂In Tc/∂p∼ - 28 Mbar-1 for all x≤0.1. Also the resistivity drop at T0 and the magnetovolume effect (ωs = 3 ΔL/L=4.2×10-3 in ErCo2) below T0 become reduced with increasing pressure. The latter is reflecting reduction of the Co moment gained below T0. © 1997 American Institute of Physics.