  On a lattice composed of triangular plaquettes where antiferromagnetic
exchange interactions between localized spins cannot be simultaneously
satisfied, the system becomes geometrically frustrated with magnetically
disordered phases remarkably different from a simple paramagnet. Spin liquid
belongs to one of these exotic states, in which a macroscopic degeneracy of the
ground state gives rise to the rich spectrum of collective phenomena. Here, we
report on the discovery of a new magnetic state in the heterostructures derived
from a single unit cell (111)-oriented spinel CoCr2O4 sandwiched between
nonmagnetic Al2O3 spacers. The artificial quasi-two-dimensional material
composed of three triangle and one kagome atomic planes shows a degree of
magnetic frustration which is almost two orders of magnitude enlarged compared
to the bulk crystals. Combined resonant X-ray absorption and torque
magnetometry measurements confirm that the designer system exhibits no sign of
spin ordering down to 30 mK, implying a possible realization of a quantum spin
liquid state in the two dimensional limit.
