Magnetocaloric effect and critical field analysis in Eu substituted La 0.7-x Eu x Sr 0.3 MnO 3 (x = 0.0, 0.1, 0.2, 0.3) manganites

Vadnala, Sudharshan and Asthana, Saket (2018) Magnetocaloric effect and critical field analysis in Eu substituted La 0.7-x Eu x Sr 0.3 MnO 3 (x = 0.0, 0.1, 0.2, 0.3) manganites. Journal of Magnetism and Magnetic Materials, 446. pp. 68-79. ISSN 0304-8853

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Abstract

In this study, we have investigated magnetic behavior, magnetocaloric effect and critical exponent analysis of La0.7-xEuxSr0.3MnO3 (x = 0.0, 0.1, 0.2, 0.3) manganites synthesized through solid state reaction route. The crystallographic data obtained from refinement of x-ray diffraction patterns reveal that crystal structure changes from rhombohedral (for x = 0.0) to orthorhombic (for x ≥ 0.1). The average ionic radius of A-site is decreased from 1.384 Å (for x = 0.0) to 1.360 Å (for x = 0.3) with Eu3+ substitution which in turn decreases the Mn-O-Mn bond angles. Magnetization measurements are performed in the vicinity of TC to determine magnetocaloric effect (MCE) and critical field behavior. The maximum magnetic entropy change View the MathML source(ΔSMmax) (forμ0ΔH=6Tμ0ΔH=6T) increases with the Eu3+ substitution from 3.88 J/kg. K (for x = 0.0) to 5.03 J/kg. K (for x = 0.3) at the transition temperature. The critical field behaviour of compounds was analysed using various methods such as modified Arrott plots, Kouvel-Fisher method and critical isotherm to determine critical temperature and critical exponents (β,β,γγ andδδ). The obtained critical exponents are in good accordance with scaling relation. The temperature dependence of the order parameter n,n, for different magnetic fields, is studied using the relation ΔSMαHn.ΔSMαHn. The values of nn are found to obey the Curie-Weiss law for temperatures above the transition temperature. The rescaled change in entropy data for all compounds collapses into the same universal curve, revealing a second order phase transition.

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