Ajuste da magnetização e calor específico de ligas de íons terras raras na presença de campo elétrico cristalino

• Ano de defesa: 2016
• Autor(a) principal: Santos, José Anselmo da Silva
• Orientador(a): Salazar, Nelson Orlando Moreno
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Sergipe
• Programa de Pós-Graduação: Pós-Graduação em Física
• País: Brasil
• Palavras-chave em Português: Física; Campo elétricos cristalino; Intermetálicos a base de terras raras; Interação de campo molecular; Magnetização; Entropia; Calor específico
• Palavras-chave em Inglês: Crystalline electric field; Rare-earth intermetallic; Molecular field interaction; Magnetization; Entropy; Specific heat
• Área do conhecimento CNPq: CIENCIAS EXATAS E DA TERRA::FISICA
• Link de acesso: https://ri.ufs.br/handle/riufs/5370

In this dissertation we have modeled the magnetic and thermal properties of rareearth intermetallic compounds by using a molecular field model. For this purpose we begin with a Hamiltonian that considers the crystalline electric field interaction and the exchange interaction between the rare earth ions treated in the approach molecular field. We developed a computer program to determine the eigenvalues and eigenvectors with which determine the magnetization, internal energy and hence the specific heat of the system. In principle we have considered systems with localized magnetism due to 4f electrons and an anisotropic exchange interaction. To test our program we have performed fittings of magnetization and specific heat data for the three families of intermetallic compounds RNi5 (R = Dy, Er, Ho, Pr, Tb), RRhIn5 (R = Ce, Er, Nd, Pr, Tm) and R3Co4Sn13 (R = La, Ce, Nd, Gd, Pr) and the HoZn and TmCd alloys. In RNi5 ferromagnetic family we got the best fittings, in RRhIn5 antiferromagnetic family the fittings provided molecular field constant very diferent much from the values found in the literature. In R3Co4Sn13 antiferromagnetic family we have gotten reasonable fits, while the TmCd and HoZn compounds the fits wore very good, because they are ferromagnetic. We concluded that even with the limitations, the molecular field model is efficient to study ferromagnetic rare earth intermetallic compounds.