Disorder in condensed matter systems: proton spin lattice relaxation study of the mixed systems of betaine phosphate and glycine phosphite, BPxGPI(1−x)
✍ Scribed by M. N. Ramanuja; K. P. Ramesh; J. Ramakrishna
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 327 KB
- Volume
- 45
- Category
- Article
- ISSN
- 0749-1581
- DOI
- 10.1002/mrc.2095
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
Proton NMR relaxation measurements have been carried out in the mixed system of antiferroelectric (AFE) betaine phosphate (BP) and ferroelectric (FE) glycine phosphite (GPI), BP~x~GPI~(1−x)~, at 11.4 and 23.3 MHz from 300 to 100 K for x = 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8. The temperature dependence of spin lattice relaxation (SLR) time follows the BPP model in the parent compounds, while the Larmor frequency dependence of T~1~ in the mixed system is rather unusual. The T~1~ curve exhibits different slopes for the low‐temperature wings at the two frequencies, which is a clear experimental evidence of the presence of different methyl groups with different activation energies (E~a~), indicating disorder. For x = 0.3 and 0.4, biexponential recovery of magnetization has been observed below 190 K, showing that the degree of disorder varies with the concentration. The temperature dependence of relaxation time data has been interpreted in terms of NH~3~, trimethyl ammonium and methyl group reorientations. Copyright © 2007 John Wiley & Sons, Ltd.