A Thermodynamic Study of the HDDR Conditions in the Sm₂Fe₁₇N_x Compound

Abstract

This paper describes the relationship between hydrogen pressure and temperature (P-T curve) in the HDDR treatment of the Sm₂Fe₁₇ compound. The P-T curve suggested that the HDDR condition of the Sm₂Fe₁₇ compound is more sensitive to temperature than that of the Nd₂Fe₁₄B compound. It was also found that the HDDR treatment of the Sm₂Fe₁₇ compound has to be controlled in the hydrogen pressure range of one order lower than that of the Nd₂Fe₁₄B compound, because of its lower optimum HDDR temperature. Using the P-T curve, new HDDR treatments named v-HD and s-DR, were carried out in order to induce anisotropic feature. However, the normalized remanence of the new HDDR treated powders was around 0.52, which suggested that the powders were almost magnetically isotropic.