Critical behavior and magnetocaloric effect in La 0.67Ca 0.33Mn 1− xCr xO 3 ( x = 0.1, 0.25)

Abstract

Universal behavior of the magnetocaloric effect along with structural and critical exponent analysis in mixed manganite La 0.67Ca 0.33Mn 1 − x Cr x O 3 ( x = 0.1, 0.25), [LCMCr 0.1 and LCMCr 0.25] exhibiting second order phase transition are investigated. Structural study using Reitveld refinement of XRD patterns indicates orthorhombic structure with Pnma space group. Modified Arrott plot method has been adopted to study the critical behavior of the compounds at their transition region, which gives values of β = 0.555(6), γ = 1.17(4) and δ = 2.7096(7) at T C = 232.5 K for LCMCr 0.1 and β = 0.68 (1), γ = 1.09(3) and δ = 2.9362(4) at T C = 202.5 K for LCMCr 0.25. The values are close to those expected for mean field ferromagnets with long range order. With increase in Cr content, the temperature corresponding to the maximum entropy change as well as the magnetic transition temperature gradually shifts to low temperatures. The maximum magnetic entropy change was found to be 3.5 J/kg K for x = 0.1 and 2.2 J/kg K for x = 0.25 for a field change of 5 T. The field dependence of the magnetic entropy change is also analyzed, which shows the power law dependence namely, ∆ S M ∝ H n , n = 0.9086(5) at T C = 232.5 K and n = 0.849(7) at T C = 202.5 K for LCMCr 0.1 and LCMCr 0.25 respectively. Relative cooling power was found to be about 147 J/kg for LCMCr 0.1 and 88 J/kg for LCMCr 0.25. The field dependence of the relative cooling power for both the compounds shows a H 1+1/δ dependence with the δ values in agreement with the mean field model.