Crystal structure and magnetic properties of R(2) (Fe, M)(17+delta)

We discovered a novel compound expressed by R(2)(Fe, M)(17+delta) in the compositional range between 2-17 and 1-12. Hong-Shou Li et al. reported R(2)(Fe, M)(29) which is stoichiometric compound with monoclinic structure. These compounds show similar X-ray diffraction patterns. In this paper, syntheses of R(2)(Fe, M)(17+delta) were attempted for various rare earth elements, R and transition metals, M, and their crystal structure and magnetic properties were investigated. It was found that nonstoichiometric compound, R(2)(Fe, M)(17+delta) (delta=1.0-4.0) forms for R=Ce,Nd,Sm,Gd,Dy,Y and M=Ti,V,Mo,W. X-ray and electron beam diffraction analyses revealed that the compound has hexagonal structure with the space group of <P(6)over bar>2m. The nonstoichiometry of the compound can be attributed to the diversity in the atom orders in the c-planes. The saturation magnetization of R(2)(Fe,M)(17+delta) is independent of the kind of M-metals, however curie temperature changes as 315K(Mo), 333K(Ti), 342K(W) and 390K(V), which is similar tendency to R(Fe,M)(32) compounds. For R(2)(Fe,M)(17+delta) the saturation magnetization and curie temperature show a maximum value for Nd(126 x 10(-6)Wb . mkg(-1)) and Gd(541K) in the rare earth series, respectively.