Magnetic-field-induced transitions and the inverse magnetocaloric effect at liquid helium temperatures in the Mn1-xCoxNiGe system (0.15 ≤ x < 0.80)

Abstract

Magnetic field-induced phase transitions found in the Mn1-xCoxNiGe system (0.15 ≤ x < 0.8) at T = 5 K may differ in nature and magnitude of the saturation magnetization of the initial weakly magnetic phase. These differences also affect the phenomena accompanying the transitions, specifically, the inverse magnetocaloric effect (MCE). In the current work, the mechanisms of these phenomena are analyzed within the framework of the magnetostructural model, which takes into account the difference in the limiting values of the magnetic order parameters in competing orthorhombic and hexagonal crystal structures. As follows from the analysis performed, the features observed in Mn1-xCoxNiGe can be explained by the realization at low temperatures of a metastable orthorhombic crystal state in magnetically ordered phases with a stable high-temperature hexagonal crystal structure.