ИСТИНА

The influence of magnetic field on magnetic phase transition of MnAs single crystal was investigated. It was established, that thee are unstable crystal and magnetic structures in temperature range above Curie temperature Tc = 308 K. The shifts of Mn and As atoms from equilibrium sites at manetostructural transition were determined. The temperature change of first order magnetic phase transition under applied magnetic field was obtained. It was established that the magnitude of magnetocaloric effect ΔT ~ 13 K in temperate range close to T c in field 140 kOe. The model of superparamagnetic condition in MnAs at temperatures above T c was introduced. It was shows that around Tc besides the magnetic part of entropy the significant contribution of crystal lattice transformation arise.