DEVELOPMENT OF MANGANITE MATERIALS FOR ROOM-TEMPERA TURE MAGNETOCALORIC APPLICATIONS

Manganites of general formula ABMnO 3 (where A is a trivalent rare-earth ion and B is a divalent dopant) have interesting properties, namely colossa l magnetoresistance and their applicability as materials for active magnetic regenerators. La 0.70 Sr 0.30 MnO 3 (LSMO) is a ferromagnet presenting considerable magnetocaloric effect, with operating temperature TC~90ºC and magnetic entropy variation comparable to pure Gadolinium. We studied the LSMO system where Lanthanum ions are substituted by Erbium or Europium, effectively lowe ring the TC to near-room temperature and below. This substitution also increases the relativ e cooling power (RCP) of the materials, an effect associated to the increased magnetoelastic contribu tion to the magnetic free energy. These results permit the creation of composites or thermal cascad es of chemically similar compounds to produce an active magnetic element with a wide temperature interval of operation (from -40ºC to 90ºC). These materials can be synthesized by solid-state r eaction or by sol-gel techniques, and are relati- vely cost-effective.