  The reversal of magnetisation has been studied in a three dimensional Ising
ferromagnet by Monte Carlo simulation with Metropolis single spin flip random
updating scheme. The outer layers are considered as surface. The surface
interacts with core with a relative ferromagnetic interaction strength. The
times of reversal of the surface and that of bulk were found to be different
for different values of relative interaction strength. For weaker relative
strength surface reversal was found to be faster than that of bulk and vice
versa for stronger relative interaction strength. A critical value ($R_c$) of
relative interaction strength provides same time of reversal of surface and
bulk. This critical relative interaction strength was found to be a function of
the temperature ($T$) and applied magnetic field ($h$). The scaling relation
$R_c \sim h^{-\beta}f(Th^{\alpha})$, where, $\alpha=0.23\pm0.01$ and $\beta
-0.06\pm0.01$, was found numerically by the method of data collapse. The
metastable volume fractions, for both surface and bulk, were found to follow
the Avrami's law. The critical relative interaction strength ($R_c$) has been
found to decrease in an exponential ($e^{bx^{-1.5}})$ manner with the system
size ($L$).
