Magnetic potassium clusters in the nanographite-based nanoporous system Original Research Article

Novel antiferromagnetic (AF) potassium clusters accommodated in the magnetic nanographene-based porous network are investigated in terms of the host–guest interaction. Raman spectroscopy proves that the potassium clusters whose size is ca. 60 potassium atoms in average are subjected to a slight charge transfer with the host nanographene. This results in a significant reduction in the edge-state spins of the host nanographene. In the high temperature region above 150 K, a large susceptibility contribution of the magnetism of the potassium clusters appears upon the increase in the potassium content. This is explained by antiferromagnetically fluctuating magnetic clusters, where the spins of potassium 4 s electrons having localized nature are suggested to interact antiferromagnetically with each other. The elongated inter-atomic distance and the structural disorder in the cluster are responsible for the localized nature of the 4 s electrons. A simple model with a unique AF spin gap gives the estimate of exchange interaction to be in the temperature region of 500–800 K.