Systematic study of magnetic interactions in insulating cuprates

Abstract

The magnetic interactions in one-dimensional, two-dimensional (2D) and ladder cuprates are evaluated systematically by using small CuO clusters. We find that the superexchange interaction J between nearest neighbor Cu spins strongly depends on CuO structure through the Madelung potential, and in 2D and ladder cuprates there is a four-spin interaction J cyc, with magnitude of 10% of J. We show that J cyc has a strong influence on the magnetic excitation in the high-energy region of 2D cuprates.