Magnetic Materials Based on 3d-Rich Ternary Compounds

This chapter presents the magnetic properties of several groups of compounds. In both systems, the increase of temperature favors spin orientation in the plane normal to the c axis. The substitution of Co atoms thus stabilizes the plane spin orientation. Interstitial nitrogen atoms thus lead to an increase of both the effective hyperfine field and the isomer shift. These results indicate that the magnetic moment of iron becomes larger with an increase of nitrogen content. The Curie temperatures are systematically 40 to 50 K lower than those of R₂Fe₁₄B. This fact might be attributed to the weakening of the exchange interaction with the shortening of some Fe–Fe distances, which is due to the smaller c/a ratio and cell volume of the carbides. Observation of the maximum moment indicates that the influence of the exchange field experienced by the 4f moments is much greater than that of the crystal field, although the latter still determines the preferred direction of 4f moments.