Magnetic and electronic properties of the kagome-like RCuO2.66 compounds

In the hexagonal phase of the RCuO2.66 delafossite (R = La or Y), the Cu-Cu superexchange interactions mediated by the O atoms yield an effective Cu network topologically equivalent to a kagome lattice. For the O-content 2.66, only 2/3 of the Cu ions are magnetic. We propose a model which points out the relevance of the topology for understanding the magnetic and electronic properties of these compounds. Two models are presented, one for the insulating phase, the other based on the t-J model describing the metallic phase.