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

Experimental and theoretical results of the study of MnFeAsyP1−y (0.15 ≤ y ≤ 0.66) and Mn2−xFexAs0.5P0.5 (0.5 ≤ x ≤ 1.0) systems were analyzed in order to determine the main factors responsible for the mechanism by which antiferromagnetic phase is formed in each of the two systems. It is shown that in the case of cation substitution in the Mn2−xFexAs0.5P0.5 system the main contribution to the mechanism of changing the magnetic ordering phase type is due to a considerable change of electron filling of the magnetically active d-band. As for the MnFeAsyP1−y system with anion substitution, destabilization of the ferromagnetic phase and formation of the antiferromagnetic phase 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.