  The role of interchain hopping in quasi-one-dimensional (Q-1D) electron
systems is investigated by extending the Kadanoff-Wilson renormalization group
of one-dimensional (1D) systems to Q-1D systems. This scheme is applied to the
extended Hubbard model to calculate the temperature ($T$) dependence of the
magnetic susceptibility, $\chi (T)$. The calculation is performed by taking
into account not only the logarithmic Cooper and Peierls channels, but also the
non-logarithmic Landau and finite momentum Cooper channels, which give relevant
contributions to the uniform response at finite temperatures. It is shown that
the interchain hopping, $t_\perp$, reduces $\chi (T)$ at low temperatures,
while it enhances $\chi(T)$ at high temperatures. This notable $t_\perp$
dependence is ascribed to the fact that $t_\perp$ enhances the
antiferromagnetic spin fluctuation at low temperatures, while it suppresses the
1D fluctuation at high temperatures. The result is at variance with the
random-phase-approximation approach, which predicts an enhancement of $\chi
(T)$ by $t_\perp$ over the whole temperature range. The influence of both the
long-range repulsion and the nesting deviations on $\chi (T)$ is further
investigated. We discuss the present results in connection with the data of
$\chi (T)$ in the (TMTTF)$_2X$ and (TMTSF)$_2X$ series of Q-1D organic
conductors, and propose a theoretical prediction for the effect of pressure on
magnetic susceptibility.
