Impact of carbon insertion on the microstructure and magnetic properties of nanocrystalline Pr2Co7 alloys

Abstract In this work, we have investigated a multi-scale study of the Pr 2 Co 7 carbides. The Pr 2 Co 7 C x compounds (where x  = 0, 0.25, 0.5, 0.75, 1) were synthesized by melting pure components in stoichiometric proportion in an arc furnace followed by high ball energy milling and annealing at different temperatures. The Pr 2 Co 7 C x compounds was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Rietveld analysis of XRD diagrams showed that the nanocrystalline Pr 2 Co 7 C x compounds annealed at T  = 973 K, mainly adopt a hexagonal Ce 2 Ni 7 type structure with P6 3 mmc space group. We have shown that the lattice parameters a , c , and cell volume V increased with increasing x content. TEM images showed that the addition of carbon refined the microstructure. In fact, it was observed that the mean grain size decreased from about 40 nm, when x  = 0, to 15 nm when x  = 1. A systematic study of the intrinsic magnetic properties of these alloys was done and showed the insertion of carbon yields enhancement of the Curie temperature by 130 K for x  = 1. This is due to the hypothesis of magnetovolumic and electronic effects on these properties. All thes studied compounds are ferromagnetic. The saturation moment μ s of nanocrystalline Pr 2 Co 7 C x increases from 8.3 to 11.6 μ B /f.u with increasing C content from x  = 0 to 1. In addition, the study of extrinsic magnetic properties, shows that the coercivity of the nanocrystalline Pr 2 Co 7 C x compounds decreases with increasing carbon content. The best overall properties including a coercivity H c of 10.5 kOe and a maximum energy product (BH) max of 11.5 MGOe for x  = 0.25, have been obtained at room temperature. These magnetic properties are suitable for hard magnetic applications.