  Temperature dependence of magnetization curves of well homogenized samples of
Ce(Co$_{1-x}$Cu$_{x}$)$_5$ ($0\le x \le 0.7$), a family of representative
$4f$-$3d$ intermetallic magnets found in rare-earth permanent magnets, is
measured. A remarkable enhancement of intrinsic coercivity is observed with
$x=0.3$ and $x=0.4$, persisting to higher temperatures. This experimental
observation is theoretically attributed to an effect of electronic correlation
among $4f$-electrons. That is, an intrinsic pinning happens originating in an
anomalously enhanced magnetic anisotropy energy contributed by an order of
magnitude stronger charge-transfer process between $4f$-electrons and
$3d$-electrons, than the conventional crystal field effects. It is demonstrated
that the $4f$-$3d$ charge-transfer process depends on the direction of
magnetization in the middle of a crossover of the valence state of Ce between
CeCu$_5$ with robust Ce$^{3+}$ and CeCo$_5$ with the mixed valence state.
