Pressure and field tuning the magnetostructural phases of Mn ₃O₄: Raman scattering and x-ray diffraction studies

We present temperature-magnetic-field-and pressure-dependent Raman scattering studies of single crystal Mn₃O₄, combined with temperature- and field-dependent x-ray diffraction studies, revealing the novel magnetostructural phases in Mn₃O₄. Our temperature-dependent studies show that the commensurate magnetic transition at T₂=33 K in the binary spinel Mn₃O₄ is associated with a structural transition from tetragonal to orthorhombic structures. Field-dependent studies show that the onset and nature of this structural transition can be controlled with an applied magnetic field, and reveal evidence for a field-tuned quantum phase transition to a tetragonal spin-disordered phase for H[11̄0]. Pressure-dependent Raman measurements indicate that the magnetic easy-axis direction in Mn₃O₄ can be controlled-and the ferrimagnetic transition temperature increased-with applied pressure. Finally, combined pressure- and magnetic-field-tuned Raman measurements reveal a rich magnetostructural phase diagram-including a pressure- and field-induced magnetically frustrated tetragonal phase in the P-H (pressure-magnetic field) phase diagram-that can be generated in Mn ₃O₄ with applied pressure and magnetic field.