Magnetic monitoring of the nitriding process in Sm-Fe-Ta-based alloys

Understanding the interactions with nitrogen that happen during the processing of Sm-Fe-material is essential if we want to achieve the best magnetic properties. The magnetic behavior of Sm_13.7Fe_86.3 and Sm_13.8Fe_82.2Ta_4.0 materials during nitriding processes was investigated using a specially designed vibrating-sample magnetometer (VSM) modified with a high-temperature (up to 1000°C) vacuum-gas system. The nitriding process for the samples was performed at a heating rate of 5°C/min to 500°C and 1 bar. If the sample was previously hydrogenation-disproportionation-desorption-recombination (HDDR)-ed, the nitrogen uptake goes very smoothly; on the other hand, if the samples were not HDDR processed, the nitrogen reaction also consisted of the decomposition of SmFe₂ and SmFe₃ phases. In order to achieve good coercivities a combination of milling and the HDDR process is necessary.