Impacts of pressure to the structural, electronic and magnetic properties of Dirac semimetal EuMnBi2

We report our investigations on the effects of pressure on the electronic and magnetic properties of magnetic Dirac semimetal ${\mathrm{EuMnBi}}_{2}$ by using electrical transport, synchrotron x-ray diffraction, and x-ray absorption spectroscopy. The antiferromagnetic interaction due to the Eu magnetic moment in ${\mathrm{EuMnBi}}_{2}$ is enhanced under pressure up to $\ensuremath{\sim}3.9\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. The N\'eel temperature (${T}_{N}$) is found to disappear above 4 GPa and a new transition ${T}_{t}$ at around 29 K emerges above 6 GPa. ${T}_{t}$ remains relatively constant up to 15 GPa, above which it increases with further compression, reaching $\ensuremath{\sim}60\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ at 22 GPa. Eu $L$-edge x-ray absorption spectroscopy revealed a valence change of Eu toward a trivalent state that begins above 6 GPa, which indicates that ${T}_{t}$ is likely related to the valence transition temperature of Eu. Sign reversal of the Hall resistivity above 7 GPa suggests that the valence change of Eu also induces a Fermi surface modification.