Magnetic transition of (MnFe)yP1−xAsx prepared by mechanochemical reaction and post-annealing

(MnFe)yP1−xAsx nanocrystalline powders have been synthesized by mechanochemical reaction near room temperature from mixtures of Fe, Mn, P and As elemental powders. These pre-reacted powders were then annealed at comparatively low temperatures for 2 h to promote a field-induced first-order magnetic transition. The influences of the metal/pnictide and P/As ratios on the transition temperature and the slope of the M-T curve have been investigated. It was confirmed that the transition temperature increases with As content. It was also found that the transition temperature and the slope of the M-T curve near the transition temperature increase with metal/pnictide ratio but they decrease when the ratio is above 2.05.