  The effects of electron (Ir) and hole (Re) doping on the hybridization gap
and antiferromagnetic order have been studied by magnetization, muon spin
relaxation ($\mu^+$SR), and inelastic neutron scattering on the polycrystalline
samples of Ce(Os$_{1-x}$Ir$_x$)$_2$Al$_{10}$ ($x$ = 0.08 and 0.15) and
CeOs$_{1.94}$Re$_{0.06}$Al$_{10}$. $\mu^+$SR spectra clearly reveals magnetic
ordering below 20 and 10 K for $x$ = 0.08 and 0.15 samples respectively with a
very weak signature of oscillations of the muon initial asymmetry at very short
time scale. Our important findings are that small amount of electron doping (i)
completely suppress the inelastic magnetic excitations near 11 meV down to 2K,
which were observed in the undoped compound, and the response transforms into a
broad quasielastic response and (ii) the internal field at the corresponding
muon site is remarkably enhanced by about ten times compared with the parent
compound. On the other hand with small amount of hole (3\% Re) doping the
intensity of the inelastic magnetic excitations near 11 meV is reduced
significantly. The main origin of the observed doping effect is an extra 5$d$
electrons being carried by Ir and a hole carried by Re compared with that the
Os atom. The obtained results demonstrate a great sensitivity of the carrier
doping and provides additional ways to study their anomalous magnetic
properties.
