Effect of pressure on the electronic state in Eu-Divalent EuTIn4 (T: Ni, Pd, Pt, Au) compounds

We grew single crystals of Eu-divalent antiferromagnets EuTIn4 (T: Ni, Pd, Pt, Au) by the In-self ux method, with the constitution of Eu:T:In = 1.1:1:30. Single crystals are characteristic in shape, being long along the orthorhombic [100] direction. We measured the electrical resistivity, specific heat, magnetic susceptibility, and de Haas-van Alphen effect for these compounds, together with the electrical resistivity under pressure for EuTIn4 (T: Ni, Pd, Pt). Under pressure, the Eu-divalent electronic state is often changed into the Eu-trivalent state, revealing the valence transition. In the present experiments, the valence transition was, however, not observed even at high pressures up to 8 GPa for these compounds, but a sharp resistivity drop was observed just below the Néel temperature under pressure. This is most likely due to a change of the magnetic structure.