Magnetic field induced order–order phase transition in magnetocaloric systems Mn2−xFexAs0.5P0.5 and MnFeAsyP1−y

Abstract An analysis is presented of experimental and theoretical results of the MnFeAs y P 1− y (0.15≤ y ≤0.66) and Mn 2− x Fe x As 0.5 P 0.5 (0.5≤ x ≤1.0) systems to identify main traits that underlie the mechanism of formation of different antiferromagnetic (AF) phases in the two systems. The discrepancy between the calculated from first principles and experimental values of the magnetic moment in the ferromagnetic phase with cation substitution in the system Mn 2− x Fe x As 0.5 P 0.5 is due to the appearance of a canted magnetic structure. In this case, the emergence of an AF phase with decreasing iron concentration precedes a significant change in the electronic d -band filling. In the model of the spiral structure in the system of itinerant electrons it is shown that the stabilization of the AF phase with decreasing arsenic concentration, while maintaining the number of d -electrons, is a consequence of changes in the shape of the density of electronic states that occur with a decrease in unit-cell volume.