SPIN STRUCTURES IN INHOMOGENEOUS FRACTIONAL QUANTUM HALL SYSTEMS.

Transitions between spin polarized and spin singlet incompressible ground state of quantum Hall systems at filling factor ⅔ are studied by means of exact diagonalization with eight electrons. We observe a stable exactly half-polarized state becoming the absolute ground state around the transition point. This might be a candidate for the anomaly observed during the transition in optical experiments. The state reacts strongly to magnetic inhomogeneities but it prefers stripe-like spin structures to formation of domains. [ABSTRACT FROM AUTHOR]