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Doctoral Thesis
DOI
10.11606/T.54.1982.tde-22042014-160005
Document
Author
Full name
Jose Alberto Rodrigues Jordao
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1982
Supervisor
Committee
Souza, Milton Ferreira de (President)
Aegerter, Michel Andre
Camargo, Paulo Cesar de
Morato, Spero Penha
Panepucci, Horacio Carlos
Title in Portuguese
Estudo de defeitos elásticos em sólidos: ultra-som e relaxação dielétrica
Keywords in Portuguese
Defeitos elásticos
Relaxação dielétrica
Ultra-som
Abstract in Portuguese
Este trabalho trata de estudos realizados sobre o comportamento das fronteiras dos domínios magnéticos em mono-cristais de (Mn - Zn) Fe2 03 como também das propriedades elásticas de defeitos puntuais em mono-cristais de NaCl: NaF: M++ . Foram aplicadas técnicas do oscilador composto de Marx com controlador automático de velocidade e atenuação ultrassônica, a técnica do pulso-eco ultrassônico e corrente termo-estimulada (I.T.C.) com pressão uniaxial. Para os cristais de NaCl: NaF: M++ , determinamos a simetria e os parâmetros de relaxação que provocam os picos de ITC chamados de B e C. Foi mostrado que o pico C é devido a relaxação de uma vacância entre as posições nn em torno do eixo que passa pelos íons F- M++ , enquanto o pico B é uma relaxação envolvendo uma transição da vacância entre as posições nn e nnn. Para as ferrites as fronteiras dos domínios magnéticos comportam-se elasticamente como dislocações, mostrando uma atenuação ultrassônica que á dependente da amplitude do campo elástico
Title in English
Study of elastic defects in solids: ultrasound and dielectric relaxation
Keywords in English
Dielectric relaxation
Elastic defects
Ultrasound
Abstract in English
This work is concerned with the behavior of magnetic domain walls of (Mn - Zn) Fe2O3 single crystals, as well as, with elastic properties of point defects in NaCl: NaF: M++ single crystals. The measurements were carried out using the following experimental techniques: pulse-echo, ITC under uniaxial stress and composite oscillator of the Marx type with automatic control of velocity. For the NaCl: NaF: M ++ crystals the symmetry of the defect that gives rise to ITC peaks B and C was determined, as well as its relaxation parameters. It was shown that peak C is due to vacancy relaxation between nn positions around the axis M++F- ions while peak B is a relaxation involving between the nn and nnn vacancy positions. For the ferrites the magnetic domain walls behave elastically as dislocations therefore having an ultrassonic attenuation that is amplitude dependent on the elastic field
 
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Publishing Date
2014-06-12
 
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