Effect of nickel doping at the Mn site on the structural, magnetic and magnetocaloric properties of the Pr0.55Sr0.45Mn1−xNixO3 (x = 0.0, 0.05, 0.1 and 0.15) manganites

Abstract

The structural X-ray diffraction (XRD), magnetic, critical behavior, and magnetocaloric characteristics of polycrystalline Pr_0.55Sr_0.45Mn_1−xNi_xO₃ manganites with 0%, 5%, 10% and 15% of Ni doping were investigated in the current work. A solid-state reaction using the stoichiometric powder mixtures of binary oxides at high temperatures was employed for the synthesis of all the samples. The Rietveld refinement of the XRD patterns indicate that the compounds crystallize in an orthorhombic structure with the Pnma space group. Temperature- and field-dependent magnetization experiments show a second-order ferromagnetic (FM) to paramagnetic (PM) phase transition in all the samples. However, when the Ni (%, x) content increases from 0.00 to 0.15, the Curie temperature (T_C) decreases from 300 K to 180 K. For all the compounds, Arrott plots reveal a second-order phase transition. Using various methods, data from static magnetization measurements at the FM–PM phase transition is used to analyze the critical parameters. Using the isothermal magnetization data around T_C, the magnetocaloric effect (MCE) in terms of maximum entropy change (−ΔS^max_M) and relative cooling power (RCP) are determined using Maxwell thermodynamic relations. In a µ₀H = 5 T magnetic field shift, the highest values of magnetic entropy changes (−ΔS^max_M) are calculated to be 3.8 J kg⁻¹ K⁻¹, 1.71 J kg⁻¹ K⁻¹, 1.62 J kg⁻¹ K⁻¹, and 1.29 J kg⁻¹ K⁻¹ for 0%, 5%, 10% and 15% of Ni, respectively. The maximum relative cooling power (RCP) values for x = 0.0, x = 0.05, x = 0.1, and x = 0.15 at µ₀H = 5 T are 247 J kg⁻¹, 216 J kg⁻¹, 211 J kg⁻¹, and 215.94 J kg⁻¹, respectively. The RCP of compound (0% of nickel) = 254.1 J kg⁻¹ is 56% of the RCP value of Gd gadolinium metal. These important features make these new materials extremely promising for magnetic refrigeration from a technical standpoint.