  Enhancement of the electron spin polarization in a correlated two-layer
two-dimensional electron system at a total Landau level filling factor of one
is reported. Using resistively detected nuclear magnetic resonance, we
demonstrate that the electron spin polarization of two closely-spaced
two-dimensional electron systems becomes maximized when inter-layer Coulomb
correlations establish spontaneous isospin ferromagnetic order. This
correlation-driven polarization dominates over the spin polarizations of
competing single-layer fractional Quantum Hall states under electron density
imbalances.
