  Monte Carlo investigations of magnetization versus field, $M_c(H)$, at the
critical temperature provide direct accurate results on the critical exponent
$\delta^{-1}$ for one, two, three and four-dimensional lattices:
$\delta_{1D}^{-1}$=0, $\delta_{2D}^{-1}$=0.0666(2)$\simeq$1/15,
$\delta_{3D}^{-1}$=0.1997(4)$\simeq$1/5,
$\delta_{4D}^{-1}$=0.332(5)$\simeq$1/3. This type of Monte Carlo data on
$\delta$, which is not easily found in studies of Ising lattices in the current
literature, as far as we know, defines extremely well the numerical value of
this exponent within very stringent limits.
