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Master's Dissertation
DOI
10.11606/D.54.1979.tde-20122010-151455
Document
Author
Full name
Carlos Alberto Olivieri
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1979
Supervisor
Title in Portuguese
Medidas de tempos de relaxação de centro F em cristais de KCN.
Keywords in Portuguese
Centros F em monocristal de KCN
Interação spin-fonon
Relaxação spin-rede
Abstract in Portuguese
Realizamos medidas de tempos de relaxação de centros F em cristais de KCN, pela técnica de saturação do sinal de absorção por pulsos de microonda. Observamos um comportamento não exponencial para a recuperação da magnetização da amostra ap6so pulso. Este fato deve-se ao efeito combinado de relaxação cruzada ou difusão da magnetização pelo espectro de absorção, juntamente com a relaxação spin-rede. Medidas à 4,2 °K e 1,8 °K fornecem indícios que, ap6s algum tempo, apenas a relaxação spin-rede sobrexiste. O modelo teórico baseado na modulação da interação hiperfina e no processo direto fornece tempos menores que os obtidos experimentalmente. Isto deve-se à formação de conglomerados de centros. Também elaboramos um modelo levando em conta processo Raman, para prever tempos de relaxação spin-rede a temperaturas mais elevadas.
Title in English
Relaxation time measurements of F centers in KCN crystal
Keywords in English
F centers in KCN monocrystal
Spin-lattice relaxation
Spin-phonon interaction
Abstract in English
We measure the spin-lattice relaxation time of F centers in KCN at 1.8 and 4.2 K using the saturation recovery technique. The observed recovery is non exponential. This result is interpreted in terms of the combined effect of cross-relaxation and spin lattice relaxation. The values obtained for T1 (- sec) are found to be shorter than those calculated theoretically. This discrepancy is throught to arise from the presence of clusters. The characteristic time found from the initial part of recovery is found to be -6 sec in agreement with that found in KC for the recovery of a hole burnt in the resonance line (45). Finally the value of T1 was calculated for the Raman processes at high temperature and compared with known results.
 
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Publishing Date
2010-12-21
 
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