A proton magnetic resonance study of the one dimensional antiferromagnetic system CsFeCl₃.2H₂O
Date
2018-06-21
Authors
Rensing, Michael John
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Abstract
Proton line shapes and spin-lattice relaxation times were acquired for the easy-axis antiferromagnet CsFeCl3-2H2O. The line shapes were acquired at 250 K for a complete 360° rotation about the b axis of the crystal, and at various temperatures between 250 K and 23 K, for two orientations.
A model for the line shapes has been created based on the temperature dependance of the interaction between protons and the local magnetic field differences at each proton site. The field differences lead to symmetric line shapes whose peaks have a separation which increases as the temperature decreases. This model accounts well for the major component of the observed line shapes, provided that the proton-proton separation is increased over the separation obtained from published data. The residual portion of the observed line shapes appears to be a single line which results from water molecules which behave as though they are not part of the crystal structure.
A simple stochastic model for the behavior of the π-kink solitons has been developed and used to predict values for the proton spin-lattice relaxation times. In this model, the solitons are treated as infinitesimal non-interacting particles travelling along straight chains of Fe2+ ions at constant speed. The arrival of solitons at a randomly chosen point on the chain is a Poisson process which leads to an expression for the spin-lattice relaxation which agrees well with observations.
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Keywords
Spin-lattice relaxation, Ferromagnetism