1H NMR spin-lattice relaxation studies in Betaine phosphate (BP) - Transition from classical to quantum rotation

• Published in: Physica Status Solidi (b) 2006-07, Vol.243 (8), p.1929-1938
• Main Authors: Ramanuja, M. N., Ramesh, K. P., Ramakrishna, J.
• Format: Article
• Language: English
• Subjects: 76.60.Es; 77.84.Jd; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Nuclear magnetic resonance and relaxation; Physics
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.200541262

We report here the results of our 1H NMR spin–lattice relaxation time (T 1) studies in betaine phosphate which is ferroelectric below 86 K and antiferroelectric below 81 K. The experiments have been carried out in the temperature range 300 to 4 K, at two Larmor frequencies 11.4 and 23.3 MHz. The T 1 data (300–100 K) has been analysed using modified BPP equation based on Ikeda's model. CH3 protons are found to relax other protons via spin diffusion. The low temperature (T < 100 K) T 1 data has been analysed following Lourens model which considers the gradual transition from classical motions to quantum regime. At low temperatures, when classical processes tend to freeze, reorienting groups apparently have minute differences and hence create a distribution in the energy values (E a and E 01) and pre‐exponential factors. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)