Influence of High-Pressure Nitrogenation on the Structure, Magnetism and Microwave Absorption Properties of SmFe10Mo2

Nitrogenation of SmFe10Mo2 powders was performed in a self-made furnace under a high-purity N2 atmosphere up to 40 MPa at 500 °C. Upon nitrogenation at atmospheric pressure, the lattice parameters a and c increase by 0.5% and 2.7%, respectively, whereas the Curie temperature T C increases from 519 to 633 K. With further increasing the nitrogenation pressure to 20 and 40 MPa, the 1:12 main phase starts to decompose and a large amount of Mo and α-Fe precipitates. This leads to variation of Mo concentration in the 1:12 phase and causes a sharp decrease in T C and in the coercivity. The relative complex permittivity and permeability of paraffin–SmFe10Mo2 composites show multi-resonant behavior. After nitrogenation, the magnetic loss of the powders decreases, which may originate from the influence of eddy currents due to the increase in the particle size.