Element-specific field-induced spin reorientation and tetracritical point in MnCr 2 S 4

The ferrimagnetic spinel ${\mathrm{MnCr}}_{2}{\mathrm{S}}_{4}$ shows a variety of magnetic-field-induced phase transitions owing to bond frustration and strong spin-lattice coupling. However, the site-resolved magnetic properties at the respective field-induced phases in high magnetic fields remain elusive. Our soft x-ray magnetic circular dichroism studies up to 40 T directly evidence element-selective magnetic-moment reorientations in the field-induced phases. The complex magnetic structures are further supported by entropy changes extracted from magnetocaloric-effect measurements. Moreover, thermodynamic experiments reveal an unusual tetracritical point in the $H\text{\ensuremath{-}}T$ phase diagram of ${\mathrm{MnCr}}_{2}{\mathrm{S}}_{4}$ due to strong spin-lattice coupling.