Effect of carbonation on the structural, magnetic and magnetocaloric properties of uniaxial nanocrystalline Pr5Co19Cx compound

In this work, we have investigated a multi-scale study of Pr5Co19 carbides. The nanocrystalline Pr5Co19Cx (x = 0, 0.5, 1, 1.5) samples were prepared using two-step method: mechanical milling process and subsequent annealing at 775 °C, followed by a solid-solid reaction carbonation at 420 °C. The structural properties of Pr5Co19Cx carbides were characterized by X-ray diffraction and refinement Rietveld method. This analysis has revealed that, all samples crystallize in the rhombohedral (3R) of Ce5Co19-type structure (space group R3¯m). The lattice parameters have increased with carbon content. Due to the magnetovolume effect, the Curie temperature was enhanced by about ΔTCTC=10%. The coercivity Hc of these carbides have decreased versus x. In addition, the magnetocaloric effect (MCE) have been studied by isothermal magnetization measurements. The low field entropy change (|▵SMmax|) present a maximum of 5.2 J/kg.K for x = 0 and decreases when C content is increasing. The Arott plots and temperature dependence of the magnetization around second order magnetic transition are reported.