Self-consistent renormalization theory of spin fluctuations in paramagnetic spinel LiV2O4

摘要

A phenomenological description for the dynamical spin susceptibility$\chi({\bf q},\omega;T)$ observed in inelastic neutron scattering measurementson powder samples of LiV$_2$O$_4$ is developed in terms of the parametrizedself-consistent renormalization (SCR) theory of spin fluctuations. Compatiblewith previous studies at $T\to 0$, a peculiar distribution in ${\bf q}$-spaceof strongly enhanced and slow spin fluctuations at $q \sim Q_c \simeq$ 0.6$\AA^{-1}$ in LiV$_2$O$_4$ is involved to derive the mode-mode coupling termentering the basic equation of the SCR theory. The equation is solvedself-consistently with the parameter values found from a fit of theoreticalresults to experimental data. For low temperatures, $T \lesssim 30$K, where theSCR theory is more reliable, the observed temperature variations of the staticspin susceptibility $\chi(Q_c;T)$ and the relaxation rate $\Gamma_Q(T)$ at$q\sim Q_c$ are well reproduced by those suggested by the theory. For $T\gtrsim30$K, the present SCR is capable in predicting only main trends in$T$-dependences of $\chi(Q_c;T)$ and $\Gamma_Q(T)$. The discussion is focused on a marked evolution (from $q \sim Q_c$ at $T\to0$ towards low $q$ values at higher temperatures) of the dominant low-$\omega$integrated neutron scattering intensity $I(q; T)$.