Effect of microstrain on the magnetism and magnetocaloric properties of MnAs0.97P0.03

In the compound MnAs0.97P0.03, 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-C Around the helimagnetic-ferromagnetic transition temperature and at T-C, a large inverse magnetocaloric effect (MCE) with magnetic entropy change Delta S-m of 5.6 J/kg K at 208 K and a normal MCE with Delta S-m, of -4.4J/kg K at 253 K for a 5T field change are observed. After annealing, MnAs0.97P0.03 exhibits a large MCE near room temperature with Delta S-m of similar to 14 J/kg K for a field change from 0 to 5 T. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3695039]