Caracterização estrutural e investigação do efeito exchange bias espontâneo na perovskita dupla La1,5Sr0,5CoMn0,5Fe0,5O6

• Ano de defesa: 2021
• Autor(a) principal: Silva, Arthur Garcia
• Orientador(a): Bufaiçal, Leandro Felix de Sousa
• Banca de defesa: Bufaiçal, Leandro Felix de Sousa, Bittar, Eduardo Matzenbacher, Santana, Ricardo Costa de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Goiás
• Programa de Pós-Graduação: Programa de Pós-graduação em Fisica (IF)
• Departamento: Instituto de Física - IF (RG)
• País: Brasil
• Palavras-chave em Português: Perovskita; Exchange bias espontâneo; Fase de griffiths
• Palavras-chave em Inglês: Perovskite; Spontaneous exchange bias; Griffiths phase
• Área do conhecimento CNPq: CIENCIAS EXATAS E DA TERRA::FISICA::FISICA GERAL
• Link de acesso: http://repositorio.bc.ufg.br/tede/handle/tede/11155

In this work we describe the synthesis and characterization of the structural, eletronic and magnetic properties of La1.5Sr0.5CoMn0.5Fe0.5O6 compound. Our main focus was on the investigation of 50% of Mn to Fe substitution in La1.5Sr0.5CoMnO6, with a particular interest in the spontaneous exchange bias effect, a phenomena characterized by the shift in the magnetic hysteresis curves taken after the system bein cooled in zero magnetic field. The polycrystalline sample here investigated was syntesized by conventional solid state reaction technique and investigated by means of X-ray powder diffraction, magnetization as a function of temperature [M(T)] and magnetization as a function of magnetic field [M(H)]. The La1.5Sr0.5CoMn0.5Fe0.5O6 crystal forms in rhombohedral symmetry, space group, in agreement with results observed for similar compounds. The M(T) measurements have revealed a ferromagnetic-like transition at TC ≈ 150 K, and also indicated the presence of competing magnetic phases, which leads to the formation of ferromagnetics clusters embedded in a paramagnetic matrix at high temperature. This is a hallmark of the Griffiths Phase, here occurring in the 150 K < T < 205 K range. The M(H) curves carried after cooling the system in zero field have showed that La1.5Sr0.5CoMn0.5Fe0.5O6 exhibits the spontaneous Exchange Bias effect at low temperatures, while for the measurements carried after cooling the system in the presence of a external magnetic field it is observed a significant enhancement of the shift in the M(H) curve.