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|Type:||Artigo de periódico|
|Title:||Dependence Of The Magnetocaloric Effect On The A-site Ionic Radius In Isoelectronic Manganites|
|Abstract:||In this work, we explore the magnetocaloric and magnetic properties of isoelectronic manganites R 0. 6 Sr 0. 4 MnO 3(R La, Pr, Nd, and Sm). Upon substitution of La 3 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 341 K for La 0. 6 Sr 0. 4 MnO 3 to 126 K for Sm 0. 6 Sr 0. 4 MnO 3. Interestingly, the magnetic-entropy change increases with decreasing r A , reaching Δ S M - 8.4 J / kg K for Δ H 0 - 20 kOe for Sm 0. 6 Sr 0. 4 MnO 3. For manganites, this is a high value of Δ S M, 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. © 2013 American Institute of Physics.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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