Pressure-Induced Localization of 4<i>f</i> Electrons in the Intermediate Valence Compound SmB₆

Abstract

We report high-pressure studies of X-ray diffraction and 11B-nuclear magnetic resonance (NMR) in the intermediate-valence compound SmB6. The pressure dependence of the lattice constant was precisely determined and no anomaly was observed up to 9.1 GPa. The temperature dependence of the nuclear quadrupole resonance frequency νQ, obtained from the 11B-NMR measurements, is predominantly contributed by on-site charge distribution. Using the relationship between νQ and Sm valence at ambient pressure reported previously, we estimate the pressure dependence of the Sm valence up to 6 GPa as well. The increase in the Sm valence accelerates with pressure and reaches an increase of about 10% at 6 GPa. The pressure-induced localization of Sm \(4f\)-holes may be responsible for the long-range magnetic order under pressure.