• JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
 
  Bookmark and Share
 
 
Disertación de Maestría
DOI
10.11606/D.43.1990.tde-28042014-160122
Documento
Autor
Nombre completo
Hamilton Jose Brumatto
Instituto/Escuela/Facultad
Área de Conocimiento
Fecha de Defensa
Publicación
São Paulo, 1990
Director
Tribunal
Becerra, Carlos Castilla (Presidente)
Figueiredo, Wagner
Paduan Filho, Armando
Título en portugués
Evidencia experimental da existencia de uma linha multicritica de lifshitz no diagrama de fase MNp.
Palabras clave en portugués
Fenômenos críticos
Ponto de Lifshitz
Ponto multicrítico
Resumen en portugués
Experimentally pure Lifshitz critical behavior has only been reported in the orthorhombic magnetic system MnP which exhibits uniaxial Ising-Type Lifshitz points LP (d=3, n=l, m=l). Two LPs have been previously identified in MnP. One when the external magnetic field H was applied along the intermediate b axis, the other when IH was along the hard anisotropy axis a. Both LPs occurs roughly at the same temperature (TL ~121K) but at different values of H due to the difference in anisotropy. In this work we report on measurements made with H applied within the ab plane. Two configurations were studied: (1) with H making an angle of 20° with the b axis and (2) with H at 45° in the b (and a) axis. The observed phase diagram obtained using an AC susceptibility technique shows, near the confluence of the modulated and ferromagnetic phases with the paramagnetic phase, the same characteristics of the phase boundaries found when H is along a and also along b . The temperature at the multicritical point is TL~120K. From an analysis of the shape of the phase boundaries near TL we obtained a crossover exponent =0.61±0.02, a value that is consistent with the found for IH along the a and the b axis. This value is also consistent with the predicted theoretically from Renormalization-Group calculation. These data suggest that there is a line of LPs connecting the multicritical points found when H is along the b and a axis.
Título en inglés
Experimental evidence of the existence of a Lifshitz multicritica line in the 'MN'p phase diagram.
Palabras clave en inglés
Critical Phenomena.
Lifshitz point
multicrítico Point
Resumen en inglés
Experimentally pure Lifshitz critical behavior has only been reported in the orthorhombic magnetic system MnP which exhibits uniaxial Ising-Type Lifshitz points LP (d=3, n=l, m=l). Two LPs have been previously identified in MnP. One when the external magnetic field H was applied along the intermediate b axis, the other when IH was along the hard anisotropy axis a. Both LPs occurs roughly at the same temperature (TL ~121K) but at different values of H due to the difference in anisotropy. In this work we report on measurements made with H applied within the ab plane. Two configurations were studied: (1) with H making an angle of 20° with the b axis and (2) with H at 45° in the b (and a) axis. The observed phase diagram obtained using an AC susceptibility technique shows, near the confluence of the modulated and ferromagnetic phases with the paramagnetic phase, the same characteristics of the phase boundaries found when H is along a and also along b . The temperature at the multicritical point is TL~120K. From an analysis of the shape of the phase boundaries near TL we obtained a crossover exponent =0.61±0.02, a value that is consistent with the found for IH along the a and the b axis. This value is also consistent with the predicted theoretically from Renormalization-Group calculation. These data suggest that there is a line of LPs connecting the multicritical points found when H is along the b and a axis.
 
ADVERTENCIA - La consulta de este documento queda condicionada a la aceptación de las siguientes condiciones de uso:
Este documento es únicamente para usos privados enmarcados en actividades de investigación y docencia. No se autoriza su reproducción con finalidades de lucro. Esta reserva de derechos afecta tanto los datos del documento como a sus contenidos. En la utilización o cita de partes del documento es obligado indicar el nombre de la persona autora.
41732Brumatto.pdf (3.73 Mbytes)
Fecha de Publicación
2014-05-05
 
ADVERTENCIA: Aprenda que son los trabajos derivados haciendo clic aquí.
Todos los derechos de la tesis/disertación pertenecen a los autores
Centro de Informática de São Carlos
Biblioteca Digital de Tesis y Disertaciones de la USP. Copyright © 2001-2020. Todos los derechos reservados.