  In conventional spin glasses, magnetic interaction is not strongly
anisotropic and the entire spin system is believed to be frozen below the
spin-glass transition temperature. In La2Cu0.94Li0.06O4, for which the in-plane
exchange interaction dominates the interplane one, only a fraction of spins
with antiferromagnetic correlations extending to neighboring planes become
spin-glass. The remaining spins with only in-plane antiferromagnetic
correlations remain spin-liquid at low temperature. Such a novel partial spin
freezing out of a two-dimensional spin-liquid observed in this cold neutron
scattering study is likely due to a delicate balance between disorder and
quantum fluctuations in the quasi-two dimensional S=1/2 Heisenberg system.
