Crossover of the magnetocaloric effect and its importance on the determination of the critical behaviour in the La0.67Ba0.33Mn0.9Cr0.1O3 perovskite manganite

Abstract

The magnetic phase transition and the magnetic entropy change (−ΔSM) in the La0.67Ba0.33Mn0.9Cr0,1O3 manganite were investigated by measuring the magnetization as a function of temperature. The maximum magnetic entropy change (−ΔSM) and the relative cooling power (RCP) are found to be, respectively, 4.20Jkg−1K−1 and 238Jkg−1 for a 5-T field change, making of this material a promising candidate for magnetic refrigeration near room temperature.To investigate the nature of the paramagnetic (PM) to ferromagnetic (FM) phase transition, found to be of second-order, we performed a critical exponents study by dc-magnetization M(H,T) measurements around the Curie temperature TC, in a temperature range including the critical region |ɛ|=|T−TC|/TC⩽0.05. From the derived values of the critical exponents (β=0.380, γ=1.345), we conclude that La0.67Ba0.33Mn0.9Cr0.1O3 belongs to the three-dimensional Heisenberg class with short-range interaction. Scaling relations are obeyed, indicating renormalized interactions around TC. By investigating the field dependence of RCP and ΔSM, it was possible to evaluate the critical exponents of the magnetic phase transitions. Their values are in good agreement with those obtained from the critical exponents using a modified Arrott method.