Crystallographic and magnetic properties of fine iron nitride powders prepared by solid state reactions between iron and organic Hx(CN)-Ring compounds

Abstract

In this work morphological, crystallographic and magnetic properties of iron nitride powders prepared by room temperature mechano-chemical processing, were studied by SEM, XRD and VSM methods. Nitridation reaction occurs during ball milling of a stoichiometric mixture of αFe powder and highly reactive complex amine compounds: piperazine, pyrazine and pyrazole in the molar ratio 3:1 (Fe:N). The amount of nitride phase produced, depends on milling time, annealing temperature and on the chemical reactivity of the amine compound with iron. Calculation of crystal lattice parameters show that prepared nitrides are similar to stoichiometric Fe₃N hcp type structure. Lattice expansion was found for hexagonal planes due to increase in nitrogen concentration. Magnetic hysteresis parameters were found to be very sensitive to changes in chemical composition. As the amount of nitrogen increases magnetic remanence and coercivity increase but magnetization and calculated average magnetic moment per Fe atom decrease.