Measurement Methods Of The Magnetocaloric Effect And The Magnetic Thermal Properties Of Magnetic Refrigeration Material

Magnetic refrigeration based on the magneto-caloric effect （MCE）,compared with the conventional gas-compression refrigeration, due to itspotential impact on high efficiency, energy savings, small volume and lessnoise, attracted people in the research and exploration. In recent years,potential room-temperature magnetic refrigeration candidate materialsbecame the research object, but larger magneto-caloric effect was oftenfound in ferromagnetic to paramagnetic first-order phase transition in themagnetic materials. Searching for proper room-temperature magneticrefrigeration materials oughted to have larger magnetic-entropy change andlarger temperature change, but the larger magnetic-entropy change andlarger temperature change were not certainty a good magnetic refrigerationcapacity. Because first-order phase transition materials involved a more andless thermal hysteresis, and which was an unfavourable magneticrefrigeration efficiency. However, secondary phase transition had relativelylow magneto-caloric effect, but it had larger magnetic refrigerating capacity,because it had not thermal hysteresis loss, which was board half peak wider.The results show that Mn_1.25Fe_0.75P_1-xSi_x（x=0.50,0.52,0.54,0.56,0.58,0.60） series alloys mainly phase is Fe2P-type hexagonal structure with space group P62m. The Si content is not the same, the alloy samples existed asecond phase of FeSi-type （space group P213）. With the increase of Sicontent, the lattice parameter a increasing trend, c and c/a graduallydecreasing. The Curie temperature was linearly decreasing and thermalhysteresis （ΔThys） linearly decreasing （from6.1K to3.0K）. When the contentof Si is0.58, the maximal isothermal magnetic-entropy change of alloysample （-ΔSmax） reduces8.6J/kgK in a field change from0to1.5T, and theseries of alloy samples with the maximal relative cooling power is102.4 J/K。The results show that Mn_1.35Fe_0.65P_0.45Si_0.55B_x（x=0.00,0.01,0.02,0.03,0.04） series alloys mainly phase is Fe2P-type hexagonal structure with space group P62m. With the increase of B content, the lattice parameter aincreasing trend, c and c/a gradually decreasing and volume （V） basicallyunchanged. By the VSM magnetic measurement, the Curie temperature Tcof the alloy sample gradually increased which was increased from228K to315K. The maximal isothermal magnetic-entropy change （-ΔSmax） in declinewere3.6,2.5,2.0,1.7,1.9J/kg·K, thermal hysteresis （ΔThys） about3K, andhalf peak wider was increasing. With the B content increasing that there isfirst phase transition change from ferromagnetic （FM） to paramagnetic （PM）to the secondary phase transition trend in the magnetic material. By the ratioof the heat capacity with temperature （Cm-T） curve, the series alloy samplesof anomalous peak gradually move to the high temperature and the jumpchange gradually weakened with the increasing B content.The results show that MnFeP0.56Si0.44Bx（x=0.00,0.01,0.02,0.03,0.04）series alloys mainly phase is Fe2P-type hexagonal structure with spacegroup P62m. With the increase of B content, the lattice parameter aincreasing, c decreasing, volume basically unchanged, a second phasedisappearing and the Curie temperature Tcincreasing from274K for x=0to351K for x=0.04, thermal hysteresis （ΔThys） linearly decreasing （from48Kto5.9K）. The maximal isothermal magnetic-entropy change reaches10.0J/kgK, and half peak wider is gradually decreasing （from28K to12K）,the maximal relative cooling power is122.3J/K. By DSC measurement alloysamples and specific heat capacity found that the Curie temperature Tcandthermal hysteresis （ΔThys） with respect to the measured value of the VSM isslightly larger. In summary, this paper is replaced toxic As elements bycheap Si or when completely replace the B element, the sample of phasestructure, magnetic properties and magneto-caloric effect was measuredusing different methods. In the vicinity of the Curie temperature pointlooking for shift fast, thermal hysteresis （ΔThys） small, temperature change wide, magnetic entropy change large, cheap, safe and non-toxic harmlessnew room-temperature magnetic refrigerant materials.