Charge-ordering and magnetoelastic coupling effects on the magnetocaloric properties of manganites

• Tipo: Artigo em Revista Científica Internacional
• Data: 2004

Autores

Reis, Mário Souza (Autor) Outra; Gomes, Angelo M S (Autor) Outra; Araújo, João Pedro (Autor) FCUP; Tavares, Pedro B. (Autor) Outra; Amaral, J. S. (Autor) Outra; Oliveira, Ivan S. (Autor) Outra; Amaral, V. S. (Autor) Outra

Revista

Título: Acta Physica Polonica A

Vol. 105

Páginas: 163-171

ISSN: 0587-4246

Editora: POLSKA AKADEMIA NAUK

Indexação

ISI Web of Knowledge - 5 Citações

Scopus - 4 Citações

Outras Informações

ID Authenticus: P-000-C08

Abstract (EN): A study of the magnetocaloric properties of La1-x-yYyCaxMnO3, La1-xCdxMnO3, and Pr1-xCaxMnO3 manganites with ferromagnetic and charge-ordered states is presented. The ferromagnetic lanthanum manganites show a negative entropy change peak DeltaS under the application of a magnetic field at the Curie temperature. However, the magnetoelastic coupling effects lead to a first-order paramagnetic-ferromagnetic transition and an increased DeltaS compared to simple ferromagnets. This effect is analyzed in the framework of the Landau theory of phase transitions which shows a comparable influence of the magnetoelastic couplings and the ordinary magnetic ordering effect. The Pr1-xCaxMnO3 system shows a rich electric and magnetic phase diagram, with a ferromagnetic insulator phase for 0.15 < x < 0.30 and coexisting charge-ordering and antiferromagnetic insulator behavior for 0.30 < x < 0.85. The magnetocaloric effect results for x = 0.25 and 0.30 show a simple ferromagnetic phase transition effect. For the samples above the onset concentration for the charge ordering (approximate to 0.30) an anomalous magnetic entropy change is observed below the charge-ordering temperature (T-co). This effect is associated with a positive contribution from the magnetic entropy change due to charge ordering, superimposed to the negative contribution due to spin ordering.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 9