resumo
Manganites of general formula ABMnO(3) (where A is a trivalent rare-earth ion and B is a divalent dopant) have interesting properties, namely colossal magnetoresistance and their applicability as materials for active magnetic regenerators. La0.70Sr0.30MnO3 (LSMO) is a ferromagnet presenting considerable magnetocaloric effect, with operating temperature T-C similar to 370 K and magnetic entropy variation comparable to pure Gadolinium. The high value of T-C makes LSMO unsuitable for room-temperature magnetic refrigeration applications, but by substituting. La With the high-magnetic moment ion Er, T-C is lowered and total magnetic entropy increases. We have found a limit of solid solubility of Er ions in LSMO, in samples prepared by either solid state or sot-gel techniques in previous works [1]. in accordance with other authors [2]. We now present a more detailed study of this limit of solubility. with more samples prepared with Er substitution close to the solubility limit and SEM microscopy clearly showing the changes in microstructure caused by the formation of a secondary ErMnO3 phase, in accordance with x-ray diffraction data and T-C variation along the series. The magnetocaloric properties of the series are also presented, showing the increase of Relative Cooling Power along the series, in applied magnetic fields up to 1 T.
palavras-chave
LA-SR MANGANITES; ER
categoria
Engineering; Materials Science
autores
Amaral, JS; Reis, MS; Araujo, JP; Mendonaca, TM; Tavares, PB; Amaral, VS; Vieira, JM
nossos autores
João Cunha de Sequeira Amaral
Investigador Auxiliar
Joaquim Manuel Vieira
Professor(a) Jubilado(a)
Mário de Souza Reis Junior
Investigador
Vitor Brás Sequeira Amaral
Professor Catedráticoagradecimentos
We would like to acknowledge M. A. Sa for assistance in magnetization measurements and also the financial support from FCT (POCI/FP/63438/2005 and POCI/CTM/61284/2004 and PhD. grant SFRH/BD/17961/2004).