Abstract

The influence of Ti-doping on the magnetic and magnetocaloric properties of La_0.67Ba_0.33Mn_0.98Ti_0.02O₃ perovskite is investigated. La_0.67Ba_0.33Mn_0.98Ti_0.02O₃ sample was prepared by ceramic route at 1400 °C. It is a cubic Pm–3m single phase and exhibits a sharp ferromagnetic–paramagnetic (FM–PM) transition at a Curie temperature T_C (314 K) which is very close to room temperature. Above T_C the data follow a Curie–Weiss law with a shift between experimental and calculated effective paramagnetic moment. The associated experimental magnetic entropy change (ΔS_M) and the relative cooling power (RCP) have been determined. The observed field dependence of ΔS_M is explained reasonably well by the Landau theory of second order phase transition. The maximum entropy change exhibits a linear dependence with the applied magnetic field. and RCP are respectively 3.21 J kg⁻¹ K⁻¹ (21.48 mJ cm⁻³ K⁻¹) and 307 J kg⁻¹ (2054 mJ cm⁻³) at 5 T, which are about 30% of pure Gd. Our results on the magnetocaloric effect (MCE) are compared favourably with reported values for other doped manganites, thus concluding that our sample can be used as a magnetic refrigerant around room temperature.

Research highlights

A low doping rate of Ti for Mn in La_0.67Ba_0.33Mn_0.98Ti_0.02O₃ perovskite tunes the Curie temperature towards room temperature which is suitable for potential applications such as the magnetic refrigeration, based on the magnetocaloric effect, the subject of this work. The maximum value of the magnetic entropy change is (21.48 mJ cm⁻³ K⁻¹) and its relative cooling power (RCP) is 307 J kg⁻¹ (2054 mJ cm⁻³) under an applied magnetic field of 5 T, and La_0.67Ba_0.33Mn_0.98Ti_0.02O₃ can thus be used as an active magnetic refrigerator in a relatively wide range of temperatures nearing 310 K, with a relatively large entropy change. The observed field dependence of ΔS_M is explained reasonably well by the Landau theory of second order phase transition.