First Principles Study on Pressure Induced Valence Transition in Eu-based Compounds

Compounds having localized 4f electrons have been extensively studied due to their interesting properties such as the Kondo effect, topological properties, and superconductivity. In particular, the effect of pressure plays a key role to induce a phase transition in these 4f compounds. For example, in magnetic 4f compounds, the critical pressure can suppress their magnetism, which is well-known as the Doniac phase diagram. In this presentation, we will focus on the tetragonal magnetic Eu-based compounds. In many cases, Eu-based compounds show divalent electronic states and magnetic ordering at low temperatures. However, it has been reported that both pressure and temperature can change these electronic states to be trivalent. Consequently, this valence transition leads to vanishing magnetism. Using first-principles calculations and model Hamiltonians, we will address the mechanism of the pressure-induced valance transition on the tetragonal magnetic Eu-based compounds.