Magnetic properties of substituted Sm2Co17−xTx compounds (T = V, Ti, Zr, and Hf)

Ternary Sm2Co17−xTx systems in which Co is replaced by V, Ti, Zr, and Hf have been studied to ascertain the efficacy of these elements in improving the permanent magnet characteristics of Sm2Co17-based magnets. Single phase materials were obtained for 0?x?1.0. X-ray diffraction measurements indicate that these compounds exhibit either the hexagonal-Th2Ni17 or the rhombohedral-Th2Zn17 structure. The lattice parameters are found to increase with x and in the order Hf<Zr<Ti<V, indicating that these elements are probably substituting for Co. Permanent magnet characteristics such as easy directions of magnetization, saturation magnetizations (M2), and anisotropy fields (HA) were measured at 295 and 77 K along with the Curie temperatures (TC). All compounds studied retain the uniaxial magnetic behavior of Sm2Co17, both at 295 and 77 K. The Curie temperatures are found to decrease with replacement of Co by V, Ti, Zr, and Hf at an approximate rate of 180, 150, 90, and 50 deg/atom, respectively. The saturation magnetic moments also decrease, with increasing x, in the order Zr<Ti<V<Hf. The striking effect of these substituents is in improving the anisotropy field, the improvement being in the order Zr≳Ti≳V≳Hf. Among all the substituents studied, Zr appears to be the most promising for permanent magnet applications.