Theoretical consideration of magnetic phase formation in MnFeAs_yP_(1-y) and Mn_(2-x) Fe_xAs_(0.5)P_(0.5) systems in the collective electron model

摘要

Experimental magnetic field dependences of magnetization in isostructural systems MnFeAs_yP_(1-y) (0.2 ≤ y ≤ 0.66) and Mn_(2-x)Fe_xAs_(0.5)P_(0.5) (0.5 ≤ x ≤ 1.1) are analyzed by using the results of calculations from the first principles and the model approach. It is shown that the basis of the electronic mechanism of changing the type of magnetic phases in the system Mn_(2-x)Fe_xAs_(0.5)P_(0.5) with cationic substitution is the change in the filling of the d-band. In the system MnFeAs_yP_(1-y) with anionic substitution the destabilization of the ferromagnetic phase and the occurrence of an antiferromagnetic one with decreasing the arsenic concentration can be caused by a change of the width of density of electronic states, owing to a considerable reduction of the unit-cell volume.