Influence of Ni content on structural, magnetocaloric and electrical properties in manganite La(0.6)Ba(0.2)Sr(0.2)Mn(1−x)Ni(x)O(3) (0 ≤ x ≤ 0.1) type perovskites

We present a detailed study on the physical properties of La(0.6)Ba(0.2)Sr(0.2)Mn(1−x)Ni(x)O(3) samples (x = 0.00, 0.05 and 0.1). The ceramics were fabricated using the sol–gel route. Structural refinement, employing the Rietveld method, disclosed a rhombohedral R3̄c phase. The magnetization vs. temperature plots show a paramagnetic–ferromagnetic (PM–FM) transition phase at the T(C) (Curie temperature), which decreases from 354 K to 301 K. From the Arrott diagrams M(2)vs. μ(0)H/M, we can conclude the phase transition is of the second order. Based on measurements of the isothermal magnetization around T(C), the magnetocaloric effects (MCEs) have been calculated. The entropy maximum change (−ΔS(M)) values are 7.40 J kg(−1) K(−1), 5.6 J kg(−1) K(−1) and 4.48 J kg(−1) K(−1), whereas the relative cooling power (RCP) values are 232 J kg(−1), 230 J kg(−1) and 156 J kg(−1) for x = 0.00, 0.05 and 0.10, respectively, under an external field (μ(0)H) of 5 T. Through these results, the La(0.6)Ba(0.2)Sr(0.2)Mn(1−x)Ni(x)O(3) (0 ≤ x ≤ 0.1) samples can be suggested for use in magnetic refrigeration technology above room temperature. The electrical resistivity (ρ) vs. temperature plots exhibit a transition from metallic behavior to semiconductor behavior in the vicinity of T(M–SC). The adiabatic small polaron hopping (ASPH) model is applied in the PM-semiconducting part (T > T(MS)). Throughout the temperature range, ρ is adjusted by the percolation model. This model is based on the phase segregation of FM-metal clusters and PM-insulating regions.