Effect of substitution of Zr on the magnetic properties of R 2Co 17 (R = Ce and Sm)

Abstract

The ternary systems Ce 2Co 17−xZr x and Sm 2Co 17−xZr x have been studied to ascertain the effect of Zr substitution on the magnetic properties. X-ray diffraction experiments show that single phase materials can be obtained only in the range of x ≤ 1 and that Zr stabilizes the hexagonal Th 2Ni 17 structure. The unit cell volume is found to increase by substitution of Zr. The Curie temperature T c decreases monotonically with increasing x at an approximate rate of 100 and 90 deg/atom for the Ce and Sm systems, respectively. The saturation magnetic moments also decrease monotonically with increasing x for both the systems. The rate of decrease is larger than that expected as a simple dilution. The anisotropy fields H A are significantly increased by Zr substitutions for both the systems, reaching 70 and 200 kOe at 77 K in the cases of Ce 2Co 16Zr 1 and Sm 2Co 16Zr 1, respectively. Among all the substituents studied until now, Zr seems to be the most effective for permanent magnet applications. Crystallographic and magnetic characteristics indicate that Zr replaces Co when the ternaries are formed.