Spiral state and persistent spin current in a system with strong Hund coupling

An effective Hamiltonian for systems with strong Hund coupling is presented, which contains a novel type of interaction between the spin current operator and the curl of two localised spins. We obtain a solution in the case that localised spins form a spiral state, In this state there exists a persistent spin current, but no electric current. In the equilibrium case, the spiral state can only exist in a one-dimensional ring or another circuit form. Our finding rules out the spiral state as a stable magnetic structure in a one-dimensional open chain or higher-dimensional system with strong Hund coupling. A possible experiment which could verify or falsify the assumption of strong Hund coupling is proposed. (C) 1997 Elsevier Science B.V.