Pressure-induced valence transition in antiferromagnet EuRh ₂Si ₂

Considering the unique properties of EuRh ₂Si ₂ from the viewpoint of the Eu valence, we have examined its physical properties under external pressure. At ambient pressure, EuRh ₂Si ₂ is an antiferromagnet with a Néel temperature T _N of 25 K, and the Eu ion is in the divalent state. The application of pressure up to 0.84 GPa slightly shifts T _N toward higher values. Under pressures higher than 1.00 GPa, an abrupt first-order valence transition emerges simultaneously with the disappearance of antiferromagnetism. For P = 1.17 GPa, the valence change associated with valence transition is roughly estimated to be ∼0.19 from the thermal expansion anomaly. The valence transition temperature T _v increases rapidly with increasing pressure. The temperature-pressure phase diagram of EuRh ₂Si ₂ is very similar to those of the other systems showing pressure-induced valence transition.