Effects of Ru substitution on the structural, magnetic and magnetocaloric properties of Pr0.68Ca0.22Sr0.1Mn1−xRuxO3 (x = 0, 0.05, 0.1 and 0.2) compounds

The structural, magnetic and magnetocaloric properties of polycrystalline Pr0.68Ca0.22Sr0.1Mn1−xRuxO3 (x = 0, 0.05, 0.1 and 0.2) compounds were studied. All the samples crystallized in an orthorhombic symmetry. A significant increase in the lattice parameters in the doped samples was attributed to the existence of Ru with a the mixed-valence state (Ru3+/Ru4+). The increase in the Curie temperature (Tc) with increasing Ru content was interpreted as Ru doping promoting the ferromagnetic interactions between Ru4+–Mn3+ and Ru4+–Mn4+pairs. The decrease in saturation magnetisation was attributed to an AFM interaction between the Ru3+–Mn3+ and Ru3+–Mn4+ pairs and smaller magnetic moments of Ru than those of Mn. The decrease in |ΔSM| (from 4.66 J kg−1 K−1 for x = 0.05 to 2.32 J kg−1 K−1 for x = 0.2 at 5 T) was attributed to the nature of phase transition (from a first-order to second-order transition) and a decrease in the saturation magnetisation.