  The electron spin resonance (ESR) spectroscopy was employed to investigate
the spin dynamics in triangular lattice antiferromagnets
CuCr$_{1-x}$Mg$_{x}$O$_2$ with $x =$ 0 and 0.02. All spectra can be well fitted
by a single Lorentzian lineshape. The analysis of the $g$ factor, the linewidth
$\bigtriangleup H$, and the ESR intensity $I$ as a function of temperature
suggests the development of significant antiferromagnetic (AFM) spin
fluctuations at temperature well above $T_N$ in both samples. However, the
evolution of the AFM spin fluctuations is different for each sample. For
undoped sample the ESR intensity $I$ is almost temperature independent between
$\sim$ 100 K and 50 K and then drops rapidly below 50 K. But for $x =$ 0.02,
the $I$ monotonously increases with cooling and reduces rapidly only below
$T_N$. These results indicate that the AFM spin fluctuations are extremely
strong in the undoped sample and appear to be suppressed upon Mg doping.
