Effect of microstrain on the magnetism and magnetocaloric properties of MnAs P

In the compound MnAs P , prepared by mechanical milling, a large microstrain of 0.68, calculated by quantitative x-ray diffraction analysis, induces a recoverable helimagnetic state at low temperatures and suppresses the temperature/field-induced orthorhombic-hexagonal phase transition. This leads to a remarkable reduction of both the thermal and the magnetic hysteresis at the Curie temperature, T . Around the helimagnetic-ferromagnetic transition temperature and at T , a large inverse magnetocaloric effect (MCE) with magnetic entropy change ΔS of 5.6 J/kg K at 208 K and a normal MCE with ΔS of -4.4 J/kg K at 253 K for a 5 T field change are observed. After annealing, MnAs P exhibits a large MCE near room temperature with ΔS of ∼14 J/kg K for a field change from 0 to 5 T. © 2012 American Institute of Physics.