Magnetocaloric effect in pristine and Bi-doped Pr_0.6Sr_0.4MnO₃ manganite

Near room temperature, magnetocaloric effect in pristine and Bi-doped Pr_0.6Sr_0.4MnO₃ manganites has been studied using in-field heat capacity measurements. The Debye temperature (θ_D) for the pristine sample was estimated to be 522 K and its value increases to 530 K for the Bi-doped sample with x=0.05. The entropy associated with paramagnetic (PM) to ferromagnetic (FM) transition is found to be 2.4 J/mol K and 2.3 J/mol K for x=0 and 0.05 compositions respectively. The estimated values of adiabatic temperature ∆T_ad for the samples with x=0 and x=0.05 are respectively 2.2 K and 1.9 K for 0-6 Tesla. The maximum isothermal change in entropy, ∆S_M for the sample Pr_0.6Sr_0.4MnO₃ with transition temperature 306 K is found to be 2.7 J/kg-K with application of external magnetic field of 2 T and for Bi-doped sample (with x=0.05) the isothermal change in entropy reduces to 2.0 J/kg-K. The calculated maximum values of the isothermal entropy changes, ∆S_M for the pristine sample, vary in the range 1.7–3.9 J/kg-K for a magnetic field change of 1–6 T. The present results suggest that these compounds can be possible candidates as magnetic refrigerants. This results in a large relative cooling power (RCP) around 93.5 J kg⁻¹ K for the pristine sample under an application of magnetic field of 2 T. On contrary, with Bi-doping, RCP decreases to 56 J kg⁻¹ K at external field of 2 T.