Peculiarities of magnetically ordered phase formation during anion and cation substitutions in MnFeAsyP1-y and Mn2-xFexAs0.5P0.5 systems

Experimental and theoretical results for MnFeAsyP1-y (0.15 <= y<= 0.66) and Mn2-xFexAs0.5P0.5 (0.5 <= x <= 1.0) systems have been analysed to determine the factors that may be a basis of the mechanism by which the antiferromagnetic phase is formed in each of the two systems. It is shown that in the case of cation substitution the main contribution to the mechanism of changing the magnetoordered phase type in the Mn2-xFe-xAs0.5P0.5 system is made by a considerable change of electron filling of the magnetically active d-band. As for the MnFeAsyP1-y system with anion substitution, the destabiligation of ferromagnetic phase and the formation of antiferromagnetic one with decreasing. As concentration may be due to the changes in the density of electronic states because of a considerable reduction of the unit cell volume.