Prolonged mixed phase induced by high pressure in MnRuP

Abstract

Hexagonally structured MnRuP was studied under high pressure up to 35 GPa from 5 to 300 K using synchrotron x-ray diffraction. We observed that a partial phase transition from hexagonal to orthorhombic symmetry started at 11 GPa. The new and denser orthorhombic phase coexisted with its parent phase for an unusually long pressure range, ΔP≈50GPa. We attribute this structural transformation to a magnetic origin, where a decisive criterion for the boundary of the mixed phase lies in the different distances between the Mn-Mn atoms. In addition, our theoretical study shows that the orthorhombic phase of MnRuP remains steady even at very high pressures up to ∼250GPa, when it should transform to a new tetragonal phase.