Enhanced magnetic refrigeration capacities in minutely Co doped Mn5-xCoxGe3 compounds

Mn5Ge3 is a ferromagnetic compound with a Curie temperature of 299 K that exhibits a large magnetocaloric effect near room temperature. Here, we have synthesized and characterized a series of Co doped Mn5-xCoxGe3 samples, in an attempt to improve the magnetocaloric properties of the system. X-ray diffraction measurements revealed that all samples exhibit the Mn5Si3-type D88 hexagonal structure at room temperature with no significant change in the lattice parameters between samples, while scanning electron micrographs showed that all samples exhibit a single compositional phase. Magnetization measurements show a decrease in Curie temperature concurrent to increasing Co concentration. Although, the magnitude of the peak magnetic entropy change stays nearly constant across the series, increased Co substitution significantly enhances the refrigerant capacity of the materials. The largest magnetocaloric effects are observed in the Mn4.85Co0.15Ge3 compound with a peak magnetic entropy change of 7.58 J/kg K and a peak refrigeration capacity of 380.32 J/kg for a magnetic field change of 50 kOe.