THE MAGNETIC ENTROPY CHANGE PROPERTIES OF LA(1-Z)R(Z)(FE1-X-YCOXALY)(13) COMPOUNDS

The structures, magnetic properties, and magnetic-entropy-changes of L a(1-z)R(z)(Fe1-x-yCoxAly)(13) (R = Ce, Pr, Nd, Sm, Gd, and Dy) were st udied. It was found that the crystal structures of La(Fe0.73-xCoxAl0.2 7)(13) maintain the LaCo13-type cubic structure. The relationship betw een saturation magnetic moments per 3d atom and the number of 3d elect rons in the compounds of La(Fe0.73-xCoxAl0.27)(13) system can be expla ined by the rigid-band model at Go-rich side and disagrees with the mo del at Fe-rich side. When 0.02 less than or equal to x less than or eq ual to 1.0, the compounds have a nearby room temperature Curie tempera ture, a high saturation magnetization and a high magnetic-entropy-chan ge. When x = 0.02 and the external magnetic field is 1.11 MA/m, the ma ximum magnetic-entropy-change of the La(Fe0.71Co0.02Al0.27)(13) compou nd is 13 kT/m(3) 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 i s 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 alpha-Fe phase. The second rare-earth elements added exist mainly in the 2:17-type phase. (C) 1996 American Institut e of Physics.