Quantum phase of the chromium spinel oxide HgCr2O4 in high magnetic fields

In this study, we have performed the magnetocaloric effect and the specific heat measurements of chromium spinel oxide $\mathrm{Hg}{\mathrm{Cr}}₂{\mathrm{O}}₄$, wherein the magnetic ${\mathrm{Cr}}³⁺$ ions form a highly frustrated pyrochlore lattice with significant spin-lattice coupling. In addition to the known magnetic-field-induced phases, our thermodynamic measurements detect a quantum phase just before the saturation of the magnetization, which has not been expected from the classical theories of the pyrochlore lattice antiferromagnet with spin-lattice coupling. Based on recent theoretical model calculation, we discuss the possibility of a spin nematic state appearing for this quantum phase.