Temperature-pressure phase diagram of the intrinsically insulating topological antiferromagnet EuCd2As2

Zintl-phase ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$ attracts much research interest because it has a potential of manifesting various ideal topological states under external parameters. Here, measurements of resistance, magnetization, Hall, and synchrotron x-ray diffraction at high pressures up to 50.8 GPa in diamond anvil cells are performed on high-quality ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$ single crystals that display a long-sought intrinsically insulating antiferromagnetic (AFM) ground state. From ambient pressure to 21.0 GPa, the AFM state of ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$ is stable and the AFM transition temperature of $\ensuremath{\sim}9.5$ K is raised linearly at a rate of $\ensuremath{\sim}1.90$ K/GPa. Meanwhile, the insulating conduction behavior is maintained despite that the whole resistance decreases remarkably. Beyond $\ensuremath{\sim}24.0$ GPa, a ferromagnetic-like metallic state shows up, due to a trigonal $P\overline{3}m1$ to monoclinic $C2/m$ structural transition, and its transition temperature of $\ensuremath{\sim}150$ K increases linearly at a rate of $\ensuremath{\sim}0.69$ K/GPa. This high-pressure magnetic metallic state dominates over the pristine AFM insulating one upon completion of the structural transition around 40 GPa. Based on the present data, we construct a temperature-pressure phase diagram for the intrinsically insulating antiferromagnet ${\mathrm{EuCd}}_{2}{\mathrm{As}}_{2}$, which offers essential insights into the pressure-dependent evolutions of magnetic and transport properties and will stimulate further exploration of the interplay among magnetism and transport, as well as nontrivial topology rooted in their interactions.