Dependence of the magnetocaloric effect on the A-site ionic radius in isoelectronic manganites

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2013-03-21
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Rocco, D. L.
Coelho, A. A.
Gama, S. [UNIFESP]
Santos, M. de C.
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In this work, we explore the magnetocaloric and magnetic properties of isoelectronic manganites R0.6Sr0.4MnO3 (R = La, Pr, Nd, and Sm). Upon substitution of La3+ by smaller rare-earth ions, the average ionic radius < r(A)> of the A-site (A = (R, Sr)) elements systematically decreases. It is found that, with decreasing < r(A)>, the magnetic-ordering temperature decreases from 341K for La0.6Sr0.4MnO3 to 126K for Sm0.6Sr0.4MnO3. Interestingly, the magnetic-entropy change increases with decreasing < r(A)>, reaching Delta S-M = - 8: 4 J/kg K for Delta H = 0 - 20 kOe for Sm0.6Sr0.4MnO3. for manganites, this is a high value of DSM, and it is related to the fact that the compound exhibits first-order magnetic transition. in contrast, the three other compounds exhibit a second order transition. the results indicate that the structural distortions caused by the decreasing < r(A)> couple the spin subsystem to the lattice, thus, inducing a first-order magnetic transition. VC 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4795769]
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Journal of Applied Physics. Melville: Amer Inst Physics, v. 113, n. 11, 5 p., 2013.
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