Microstructure And Magnetic Properties Of ?MnFeZ?₂P_0.77Ge_0.23?Z=Ni,CO? Series Compounds

With the continuous development of human society,refrigeration technology has inevitably appeared,but now the main refrigeration technology is still the use of compressor refrigeration.Nowadays,the sustainable application of energy and the improvement of energy conversion rate have been the focus of research.Magnetic refrigeration technology has the advantages of high efficiency and environmental protection,which has attracted a large number of researchers to study it.In this paper,we study the microstructure and magnetic properties of?MnFeZ?₂P_0.77Ge_0.23?Z=Ni,Co?compounds.1.Mn_1-xZ_xFeP_0.77Ge_0.23?x=0.03,0.05,0.07,0.08,0.09;Z=Ni,Co?series compounds were prepared by high-energy ball milling and solid-state-reaction sintering method.X ray diffraction patterns show that the series compounds crystallize in Fe₂P hexagonal structure of the P-62m space group.In this series of compounds,the lattice constants a,b gradually decrease and the lattice constant c gradually increases with increasing the Ni,Co doping elements.We analyzed the X ray diffraction patterns at various temperatures,it is found that the lattice constants a,b decrease,and c increase as increasesing the temperature for Mn_0.95Ni_0.05FeP_0.77Ge_0.23.23 and Mn_0.95Co_0.05FeP_0.77Ge_0.23 compounds,and they had a magnetic transition between the paramagnetic and ferromagnetic phases at 280 K and 304 K,respectively.2.Magnetic measurements were carried out in a vibrating sample magnetometer for Mn_1-xZ_xFeP_0.77Ge_0.23?x=0.03,0.05,0.07,0.08,0.09;Z=Co,Ni?series compounds.The Curie temperature decreases with the increase of the concentration of the dopant Ni,Co elements.The Curie temperature of the Mn_0.95Ni_0.05FeP_0.77Ge_0.23 and Mn_0.95Co_0.05FeP_0.77Ge_0.23compound is 284 K and 303 K,respectively.3.The X ray absorption fine structure measurements near Mn K,Fe K,Ni K,Ge K edges were carried out using synchrotron radiation at the beamline BL-9C of Photon Factory.The local structures around the Mn,Fe,Ni,Ge atoms in the MnFe_1-xZ_xP_0.77Ge_0.23?Z=Ni,Co;x=0.05,0.10,0.15?compounds have been determined.The Fe atoms occupy the 3f sites and Mn atoms occupy the 3g sites.Ni,Coelement as the main doping element occupy the 3f crystal position.