Proton spin-lattice relaxation in TMMC [(CH3)4NMnCl3

Abstract

We examine the temperature and frequency dependence of the proton spin-lattice relaxation rate $\frac{1}{{T}_{1}}$, as a probe of the electron-spin dynamics of the quasi-one-dimensional exchange-coupled paramagnet TMMC [${(\mathrm{C}{\mathrm{H}}_{3})}_{4}$ NMn${\mathrm{Cl}}_{3}$]. The rate is measured from 5.5-16 MHz and from 1.4 \ifmmode^\circ\else\textdegree\fi{}K to room temperature. An extension of Moriya's magnetic-relaxation theory to the linear-chain system, using the exact classical results for static spin-correlation functions, gives over-all good quantitative agreement between theory and experiment. A sharp minimum in $\frac{1}{{T}_{1}}$ at $T\ensuremath{\simeq}18$ \ifmmode^\circ\else\textdegree\fi{}K, an ${\ensuremath{\omega}}^{\ensuremath{-}\frac{1}{2}}$ dependence on frequency at room temperature and ${\ensuremath{\omega}}^{\ensuremath{-}\frac{3}{2}}$ at low temperature, with the external field parallel to the chain, and the frequency independence of $\frac{1}{{T}_{1}}$ at room temperature with the field perpendicular to the chain are all explained by the theory.