Hydrogen as a technological medium for the formation of nanostructures in Sm-Co ferromagnetic alloys

We present a survey of the results of application of various modes of hydrogen treatment of ferromagnetic materials based on the SmCo5 compound aimed at the formation of anisotropic nanostructures, namely, of mechanochemical milling, thermal treatment [hydrogenation, disproportionation, desorption, and recombination (HDDR)] of alloys in hydrogen, and the combination of milling in hydrogen with HDDR. It is shown that HDDR enables us to get alloys containing the SmCo5, Sm2Co17, and Sm2Co7 phases with grain sizes within the range 60-100 nm and the single-phase magnetic behavior. The anisotropic powders with microstructural grain sizes within the range 40-75 nm and coercive forces higher than 40 kOe were obtained after milling in hydrogen combined with HDDR. A combined method of processing including the procedure of milling of the alloys in hydrogen and HDDR treatment is proposed for the formation of the microstructure of ferromagnetic alloys with high dispersion and high magnetic properties. It is experimentally demonstrated that the formation of anisotropy in ferromagnetic alloys by disproportionation and recombination is possible if the residual amounts of the main phase of the alloy remain in the metal after disproportionation.