Critical Behavior, Phenomenological Model, Electrical and Dielectric Properties of La0.67−xPrxBa0.33MnO3 (x = 0.1 and 0.2) Manganites

In this study, we examined the magnetic and electrical properties of sol–gel-prepared polycrystalline manganites La_0.67−xPr_xBa_0.33MnO₃ (x = 0.1 and 0.2). The temperature-dependent magnetization reveals that as the temperature decreases, the samples undergo a second-order phase transition from the paramagnetic to the ferromagnetic state. We explore the correlation between experimental findings and theoretical analysis based on phenomenological models that effectively simulate magnetic and magnetocaloric measurements. The predicted maximum magnetic entropy change (ΔS_max) under a 5 T magnetic field is 5.8 J kg⁻¹ K⁻¹ for x = 0.1 and 3.33 J kg⁻¹ K⁻¹ for x = 0.2. Furthermore, we estimate the relative cooling power and specific heat capacity, suggesting that these compounds could be promising candidates for magnetic refrigeration at low temperatures. In addition, the electrical characteristics of La_0.67−xPr_xBa_0.33MnO₃ (x = 0.1 and x = 0.2) were investigated over a wide range of temperatures (120 to 380 K) and frequencies (40 to 10⁷ Hz) by means of impedance spectroscopy. A transition from semiconducting to metallic behavior is observed at 300 K. Charge carrier hopping between Mn³⁺ and Mn⁴⁺ ions has also been explored with regard to its effects on frequency, temperature, and composition, particularly in relation to permittivity (ε′, ε″) and dielectric loss (tan δ).