  We performed a nuclear magnetometry study on quantum Hall ferromagnet with a
bilayer total filling factor of $\nu_{\rm{tot}} = 2$. We found not only a rapid
nuclear relaxation but also a sudden change in the nuclear spin polarization
distribution after a one-second interaction with a canted antiferromagnetic
phase. We discuss the possibility of observing cooperative phenomena coming
from nuclear spin ensemble triggered by electrons with collective spin
interactions.
