The magnetic entropy change properties of La1−zRz(Fe1−x−yCoxAly)13 compounds

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Abstract
The structures, magnetic properties, and magnetic‐entropy‐changes of La1−zRz(Fe1−x−yCoxAly)13 (R=Ce, Pr, Nd, Sm, Gd, and Dy) were studied. It was found that the crystal structures of La(Fe0.73−xCoxAl0.27)13 maintain the LaCo13‐type cubic structure. The relationship between saturation magnetic moments per 3d atom and the number of 3d electrons in the compounds of La(Fe0.73−xCoxAl0.27)13 system can be explained by the rigid‐band model at Co‐rich side and disagrees with the model at Fe‐rich side. When 0.02≤x≤1.0, the compounds have a nearby room temperature Curie temperature, a high saturation magnetization and a high magnetic‐entropy‐change. When x=0.02 and the external magnetic field is 1.11 MA/m, the maximum magnetic‐entropy‐change of the La(Fe0.71Co0.02Al0.27)13 compound is 13 kJ/m3⋅K which is about half of that of metal Gd at the same external magnetic field. The saturation magnetization of the compound increases and the maximum magnetic‐entropy‐change decreases when La is substituted by Ce. The compounds in which La is substituted by other rare‐earth elements R (R=Pr, Nd, Sm, Gd, and Dy) decomposed into 1:13‐type, 2:17‐type, and α‐Fe phase. The second rare‐earth elements added exist mainly in the 2:17‐type phase.