Structural Transformation of MnAs<SUB>1-<i>x</i></SUB>Sb<SUB><i>x</i></SUB> under High Magnetic Fields

Abstract

Structural transformation induced by magnetic fields on MnAs and MnAs0.9Sb0.1 was investigated by the X-ray diffraction measurements in high magnetic fields up to 5 T. The X-ray diffraction profiles at 319 K for MnAs showed a single phase of the orthorhombic MnP-type structure in zero field, and applying a magnetic field of 3 T caused an appearance of the hexagonal NiAs-type structure. On further increase of magnetic fields, the single phase with the hexagonal structure was confirmed above 3.5 T in a forced ferromagnetic state. The X-ray diffraction profiles at 295 K for MnAs0.9Sb0.1 showed the hexagonal NiAs-type structure. However, the coexistence of two kinds of the NiAs-type structure with different lattice parameters was confirmed in the magnetic field of 2.5 T. The two phase coexistence was also confirmed in the temperature variation measurements in zero magnetic field. The lattice volume of the ferromagnetic phase was 1.1% larger than that of the paramagnetic phase. These results imply that the transition at TC for MnAs0.9Sb0.1 is of the first-order.