Structure, Magnetic Properties And Magnetocaloric Effect Of Ni-Mn-Sb Alloys And CeFe₂ Alloys

Nowadays, due to requirements of environment protection, magnetic refrigeration technology becomes more popular. It is a high-tech and environmental protecting technique in the field of refrigeration, which is a potentially promising technique. Magnetic refrigeration is based on magnetocaloric effect (MCE), which is intrinsic to any magnetic material. Magnetic refrigeration is achieved through the magnetic entropy change, which is caused by the magnetic moment order changing due to appling magnetic field. Therefore, the key of the technology is to obtain the giant MCE materials, In this paper, we investigated the structure, magnetic properties and MCE of Ni49-xZnxMn39Sb12(x=0,2,4) and Ce1-xDyxFe1.9(x=0,0.02,0.05,0.1, 0.15). Besides, a large entropy change was obtained. Also, the structures of the other 3 systems were investigated.Ni49-xZnxMn39Sb12 (x=0,2,4) alloys were prepared by magneto-controlled are furnace under a high-purity argon atmosphere, followed by homogenization. XRD analysis shows that Ni49-xZnxMn39Sb12 (x=0) alloys were orthogonal structure of four-layer 4O(22). The samples of x=2,4 were both L21 cube structure, x=0 sample exhibits the transition from ferromagnetism to paramagnetism at 299 K, together with the martensitic transition at 352 K. Sample of x=2 displays the martensitic transition at 291 K, Curie temperature is 348 K. Sample x=4 exhibits the martensitic transition at 265 K and Curie temperature is 363 K. A large magnetic entropy change, i.e.13.3 J/kg·K, sample of x=2 at 296 K, can be obtained in an applied field of 5 T. This is due to the transition of the low-temperature weak ferromagnetic martensitic phase to the high-temperature and strong ferromagnetic austenite one.Ce1-xDyxFe1.9 (x=0,0.02,0.05,0.1,0.15) alloys were prepared by magneto-controlled are furnace under a high-purity argon atmosphere, followed by homogenization. The analysis of XRD reveals that the compounds with x=0,0.02, 0.05,0.1,0.15 are all MgCu2-type Laves phase. Magnetic measurements indicate that with the Dy substitution of Ce, the curie temperatures of Ce1-xDyxFe1.9 increase. A large magnetic entropy change, i.e.31.7 J/kg-K, sample of x=0 at 234 K, can be obtained in an applied field of 5 T. However, with the Dy substitution of Ce, the magnetic entropy is reduced as the Curie temperatures rise. A magnetic entropy change, i.e.17.1 J/kg-K, sample of x=0.1 at 304 K, can be obtained in an applied field of 5 T.Mn36-xNi29Ge35+x (x=0,3,6), Mn36Ni29-xCoxGe35 (x=0,4,8) and Ni45Mn44Sn10X (X=Sn, Ge, Sb, In) were prepared by magneto-controlled are furnace under a high-purity argon atmosphere, followed by homogenization. XRD analysis shows that Mn36-xNi29Ge35+x (x= 0,3,6), Mn36Ni29-xCoxGe35 (x=0,4,8) and Ni45Mn44Sn10X (X=Sn, Ge, Sb, In) were L21 cube structure. The magnetic measurements will be conducted.