  We report on the emergent magnetic state of (111)-oriented CoCr2O4 ultrathin
films sandwiched by Al2O3 in the quantum confined geometry. At the
two-dimensional crossover, polarized neutron reflectometry reveals an anomalous
enhancement of the total magnetization compared to the bulk value. Synchrotron
x-ray magnetic circular dichroism (XMCD) demonstrates the appearance of
long-range ferromagnetic ordering of spins on both Co and Cr sublattices.
Brillouin function analyses further corroborates that the observed phenomena
are due to the strongly altered magnetic frustration, manifested by the onset
of a Yafet-Kittel type ordering as the new ground state in the ultrathin limit,
which is unattainable in the bulk.
