O efeito magnetocalórico na série Gd(1-y)Pr(y)Ni2

• Autor(a) principal: Lopes, Pedro Henrique de Oliveira
• Data de Publicação: 2014
• 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/1/12946
• topic: Magnetocaloric effect; Crystalline electric field; Efeito magnetocalórico; Campo elétrico cristalino; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DA MATERIA CONDENSADA

In general, the magnetocaloric effect (MCE) is characterized by the adiabatic temperature change, (ΔTad) , and the isothermal entropy change, (ΔST) , under changes of the magnetic field intensity. Due to technological applications of the MCE on magnetic refrigeration, which do not present hazardous effects to the environmental and has the potential to lower energy consumption, the interest on the MCE had grown over the years . In this work, we have studied the magnetic and magnetocaloric properties in the series Gd(1-Y)Pr(Y)Ni2 with Y = 0, 0.25, 0.5, 0.75 and 1. The RNi2 (R = Rare-earth) compounds crystallize in the cubic laves phase, which makes the cubic CEF an appropriate framework to describe the magnetism on these compounds . Besides CEF, the model Hamiltonian includes contributions of the Zeeman effect, and the indirect exchange interactions among Gd-Gd, Gd-Pr and Pr-Pr ions. It is worth noticing that the GdNi2 presents a ferromagnetic arrangement with transition temperature around 78 K and the PrNi2 compound is paramagnetic. The temperature dependences of the magnetocaloric potentials were simulated and compared with the experimental data. Furthermore, the influence of the magnetic field direction on the magnetocaloric quantities was theoretically investigated.