Critical behavior and magnetocaloric effect in La_(0.67)Ca_(0.33)Mn_(1-x)Cr_xO_3 (x = 0.1, 0.25)

摘要

Universal behavior of the magnetocaloric effect along with structural and critical exponent analysis in mixed manganite La_(0.67)Ca_(0.33)Mn_(1-x)Cr_xO_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 5 = 2.9362(4) at T_c = 202.5 K for LCMCro.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.