Structural, magnetic and magnetocaloric properties of La_0.7Ca_0.2Sr_0.1Mn_1−xCr_xO₃ compounds with x = 0, 0.05 and 0.1

Highlights: • The samples crystallize in the rhombohedral structure with the R3^¯c space group. • Enhancement of T_C for the rhombohedral samples. • The relative cooling power increases with Cr-doping. • All samples exhibit a large magnetocaloric effect. • High values of the magnetoresistance in all samples. - Abstract: Structural, magnetic and magnetocaloric properties of La_0.7Sr_0.1Ca_0.2Mn_1−xCr_xO₃ compounds with x = 0, 0.05 and 0.1 have been investigated to shed light on Cr-doping influence. X-ray diffraction studies show that all samples crystallize in the rhombohedral symmetry with R3^¯c space group. Rietveld refinement structure shows that the insertion of Cr in Mn network modifies the structural parameters such as the volume, Mn–O–Mn angles and the Mn–O bond length. The substitution of Mn by Cr decreases the 2p-3d hybridization between O and Mn ions, reduces the bandwidth and increases the electron–phonon coupling. The investigation of magnetic and magnetocaloric properties reveals that the samples exhibit a paramagnetic(PM)–ferromagnetic (FM) transition with decreasing Curie temperature (T_C) from 294 K to 255 K when Cr doping level increases. The magnetic entropy change (ΔS_M^max) also decreases from 6.20 J kg⁻¹ K⁻¹ for x = 0 to3.80 J kg⁻¹ K⁻¹ for x = 0.1, while the relative cooling power (RCP) increases from 234.5 to 240 J kg⁻¹, respectively, under a magnetic field of 5 T. These outcomes suggest that Mn-site Cr doping inhibits the enhancement of the magnetocaloric effect in some perovskite manganites. This is explained by the weakening of the ferromagnetic double-exchange interaction between Mn³⁺ and Mn⁴⁺ ions