Investigação do efeito magnetocalórico convencional e anisotrópico no sistema Er(1-y)Ho(y)N

• Autor(a) principal: Alvarenga, Thiago da Silva Teixeira
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UERJ
• Texto Completo: http://www.bdtd.uerj.br/handle/1/12920
• topic: Magnetocaloric effect; Anisotropic magnetocaloric effect; Rare earth intermetallic compounds; Crystalline field; Efeito magnetocalórico; Campo cristalino; Mononitretos com terras-raras; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DA MATERIA CONDENSADA

The magnetocaloric effect, magnetic refrigeration base, is characterized by two quantities: the isothermal entropy change (ΔST) and the adiabatic temperature change (ΔTad) which can be obtained through variations in the intensity of a magnetic field applied. In systems which present magnetic anisotropy, one can define anisotropic magnetocaloric effect, which, by definition, is calculated through the variation the direction of application of a magnetic field whose intensity remains fixed. In the materials of our interest, the magnetocaloric effect is studied theoretically starting from a model Hamiltonian which takes into account the magnetic lattice (that can be composed of several magnetic sublattices coupled), crystalline lattice and the dynamics of the conduction electrons. In the magnetic hamiltonian are considered the exchange interactions, Zeeman and crystalline electrical field (this latter responsible for the magnetic anisotropy). Recently, we studied the conventional magnetocaloric effect and anisotropic magnetocaloric effect in mononitrides compounds with rare earths, namely: o(Y)Er(1-Y)N for concentrations y= 0,1,0.5 e 0.75 . Comparisons between our theoretical results and experimental data for EMC were quite satisfactory [26].Furthermore, several theoretical predictions how to the existence of a phase ferrimagnetic in the system Ho(y)Er(1-y)N (for concentration ) and spin reorientations in the sublattices of Ho and Er were made [25].