Pressure-Induced Electronic Collapse and Semiconductor-to-Metal Transition in EuO

Abstract

Pressure-volume data for EuO to 400 kbar are presented. An electronic collapse in the Eu ion involving the promotion of a $4f$ electron to the $5d$ state occurs near 300 kbar at room temperature. The structure remains NaCl type in this transformation. The transition appears to be first order and is from semiconductor to the metallic state. The collapsed NaCl phase undergoes a phase change to the CsCl-type structure near 400 kbar.