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Doctoral Thesis
DOI
10.11606/T.43.1982.tde-15082012-145754
Document
Author
Full name
Carlos Seihiti Orii Yokoi
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1982
Supervisor
Committee
Salinas, Silvio Roberto de Azevedo (President)
Becerra, Carlos Castilla
Perez, Jose Fernando
Qualifik, Paul
Tsallis, Constantino
Title in Portuguese
Estudo de alguns modelos para sistemas magnéticos modulados na presença de um campo magnético
Keywords in Portuguese
Campo magnético
MnP
Modelo de ising
ponto de Lifshitz
Sistema magnético
Abstract in Portuguese
Dois modelos descrevendo sistemas magnéticos modulados são estudados na presença de um campo magnético. Na primeira parte consideramos um modelo de Ising com interações competitivas numa única direção espacial (modelo ANNNI). A superfície crítica, a linha tricrítica, a estrutura das fases moduladas, e os diagramas de fases são determinados na aproximação de campo médio. O comportamento crítico e tricrítico é analisado através do método de Grupo de Renormalização. Na segunda parte estudamos um modelo adequado à descrição do composto MnP. Cálculos realizados na aproximação de campo médio e através do método de Grupo de Renormalização contribuem para esclarecer os resultados experimentais acerca do ponto de Lifshitz observado neste composto.
Title in English
Study of some Models for the magnetic systems in the presence of a modulated magnetic field
Keywords in English
Ising model
Lifshitz point
magnetic field
magnetic system
MnP
Abstract in English
Two models describing modulated magnetic systems are studied in the presence of a magnetic field. The first part is dedicated to the study of an Ising model with competing interactions along one of the spatial directions (ANNNI model). The critical surface, the tricritical line, the structure of the modulated phases, and the phase diagrams are determined in the mean field approximation. The critical and the tricritical behaviour is analised by the Renormalization Group method. The second part is concerned with a model suitable for the description of the compound MnP. Calculations carried out in the mean field approximation and through the Renormalization Group method provide a better understanding of the experimental results on the Lifshitz point observed in this compound.
 
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46107Yokoi.pdf (44.37 Mbytes)
Publishing Date
2012-08-15
 
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