Hiroshi Maeda1, Mitsunori Sato1 and Mitsuru Uehara1
1Tsukuba Laboratories, National Research Institute for Metals, Ibaraki
For Ni2(Mn1-xMx)Sn with M=V and Nb (x=0.1, 0.2, 0.3 and 0.4), and Mn3-y-zCryAlC1+z (y=0 and z=-0.16, -0.08 and 0, and z=0.1 and y=0, 0.06, 0.15 and 0.26) the Curie temperature Tc, the saturation magnetization Ms, and the magnetic entropy Δ SM near Tc have been studied. The values of Δ SM are determined from the measured magnetization-temperature curves. As x or (y+z) increases, the values of Tc linearly decrease from room temperature to about 200 K, and Ms also linearly decreases. The largest values of the maximum magnetic entropy (Δ SM)Max obtained at x=0.1 to 0.2 in the formar system and at y=0 and z=0.1 in the latter one reach about half of that of Gd, and (Δ SM)Max gradually decreases with increasing x or y. Furthermore, the values of Δ SM are calculated using a molecular field approximation. The calculated values are in agreement with the experimental ones for the materials with low x or y, but the difference between the both values becomes large with increasing x or y, and particularly in the formar system with M=Nb and in the latter one with z≤0.
magnetic refrigerants, Heusler alloys, manganese compounds, nickel compounds, Curie temperature, saturation magnetization, magnetic moment, magnetic entropy, molecular field approximation
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