Magnetic order versus intermediate valence in Eu(Pd 1− xAu x) 2Si 2 under high pressure

Abstract

The magnetically ordering compound Eu(Pd 0.7Au 0.3) 2Si 2 has been studied by 151 Eu Mössbauer effect at 300 and 4.2 K under pressure up to 3.9 GPa. Above ≈ 2.7 GPa the Eu-ion changes its valence from divalent to intermediate valent (IV) character. The results indicate an increase of the magnetic hyperfine field B eff in the valence region of 2.0 < υ <2.1. For υ > 2.1 B eff vanished abruptly displaying a collapse of the magnetic order (MO). It is shown, that MO and IV can coexist in the valence region 2.0 < υ < 2.2. The experimental results are compared with several theoretical models describing a possible coexistence of MO and IV.