Magnetic properties of nanostructured Fe92P8 powder mixture

Structural and magnetic properties of nanostructured Fe92P8 (wt.%) powder mixture prepared by mechanical alloying were investigated by X-ray diffraction (XRD), Mössbauer spectrometry and magnetic measurements. The crystallite sizes were found to decrease with milling time to the nanometer scale (6-14 nm). Milling for 21 h gives rise to a mixture of: (i) a two-bcc α-Fe structure with the same lattice parameter but different microstructural (crystallite size, microstrain) and hyperfine parameters (magnetic field, isomer shift), (ii) Fe3P nanophase and (iii) a small amount of a paramagnetic FeP phosphide phase, not exceeding 2%. Furthermore, the temperature dependence of the magnetic susceptibility measurement reveals the presence of two magnetic phases with different Curie temperatures, Tc1 and Tc2. One Curie temperature is nearly constant (Tc1 = 867 K) during the milling process, while the other one (Tc2) is milling time dependent. Annealing at a temperature of 210 °C for half an hour leads to the formation of the FeP phosphide in addition to an α-Fe(P) solid solution and the Fe3P nanophase.