Structural features of the ferromagnetic order formation in the Mn$_{1-x}$Cr$_{x}$NiGe system

Within the phenomenological model of the interacting parameters of magnetic and structural orders, magnetic and structural transitions in magnetocaloric alloys of the Mn$_{1-x}$Cr$_{x}$NiGe system are analyzed. Based on the calculated isobaric temperature dependences of the parameters of magnetic and structural orders, a magnetic susceptibility jump in the first-order structural transition region is predicted and confirmed experimentally; the change in the magnetic ordering type during the approach of magnetic and structural transitions is justified. The change in the phase transition type during the reverse change in the temperature and magnetic field, which is observed in a number of samples of the system under study, is explained. The efficiency of the use of the transitions induced by the magnetic field in magnetocaloric applications is analyzed.