Continuous pressure-induced valence and magnetic transitions in EuMnSb2

EuMnSb2 is a unique and promising compound with complex magnetism (Eu and Mn sublattices) to realize magnetic control of topological quasiparticles. By applying pressure (P) to this system, we have observed a continuous pressure-induced valence change from Eu2+ to Eu3+. Remarkably, despite the significant valence change in Eu ions, an extremely large increase in the magnetic ordering temperature (TN,Eu) from 21 K at ambient pressure to 180 K at 28.4 GPa is detected. The substantial enhancement in TN,Eu is likely the consequence of the reduced distance between neighboring Eu ions and the enhanced indirect exchange interaction through increased 4 f-5d mixing under pressure. Furthermore, TN,Eu(P) shows a discontinuous change above 8 GPa, although the orthorhombic crystal structure remains stable. Our experimental data indicate the record high value in the magnetic hyperfine field of 151Eu, reaching 74.1 T at 28.4 GPa and 26 K. These unusual electronic and magnetic transitions revealed by pressure highlight that EuMnSb2 is a rich magnetic topological semimetal candidate for investigating a multitude of strong correlations.