Research of the preparation technic and magnetic properties of Mn_(2-x) Fe_x P_(1-y) Gey magneto-caloric materials

Mn2-xFexP1-yGey (x=0.8,0.9,y=0.2,0.24,0.26) magneto-caloric compounds have been prepared by mechanical alloying(MA)and subsequent spark plasma sintering (SPS) technique.XRD,neutron diffraction and SEM were used to analysis the influences of the ball milling time,sintering temperature,pressure and time on the phase formation systematically.A stable preparation technique for the MnFePGe magneto-caloric materials was established.It was found that the quantity of the impurity decreased as the temperature increasing.The magnetic phase transition process and magnetocaloric properties of the Mn2-xFexP1-yGey alloys were investigated by DSC and SQUID.The compound Mn1.2Fe0.8P0.74Ge0.26 was expected to be a suitable candidate for a magnetic refrigeration applications with a small thermal hysteresis (3K),a Curie temperature close to room temperature (277.4K),and a large magnetocaloric effect (ΔSDSC=21.5J/(kg·K).