Structure, magnetic properties and magnetocaloric effects of Fe50Mn15-x Co x Ni35 alloys

Fe50Mn15-x Co (x) Ni-35 (x=0, 1, 3, 5, 7) alloys were prepared by arc melting under purified argon atmosphere. The ingots were homogenized at 930A degrees C for 90 h followed by water quenching. The crystal structure, magnetic properties and magnetocaloric effects of the alloys were studied by X-ray diffraction (XRD) and MPMS-7-type SQUID. The results show that all samples still maintained a single gamma-(Fe, Ni)-type phase structure. With the increase of the content of Co, the Curie temperatures of these alloys increased and exhibited a second-order magnetic transition from ferromagnetic (FM) to paramagnetic (PM) state near Curie temperature. The maximum magnetic entropy change and the relative cooling power of Fe50Mn10Co5Ni35 alloy was 2.55 J/kg center dot K and 181 J/kg, respectively, for an external field change of 5 T. Compared with rare earth metal Gd, Fe50Mn15-x Co (x) Ni-35 series of alloys have obvious advantage in resource price; their Curie temperatures can be tuned to near room temperature, maintain a relatively large magnetic entropy change at the same time and they are a type of potential magnetic refrigeration materials near room temperature.