Pseudodipole interaction of ions with nonzero orbital angular momenta

It is shown that the direct exchange interaction of ions possessing electrons (holes) with orbital angular momenta L and l always contains a contribution V0L.l + V-1 (L.(B) over cap)((B) over cap. l), where (B) over cap is a unit vector along the bond connecting the ions. As a result, taking the spin-orbit interaction into account gives rise to a pseudodipole interaction of the spins (total angular momenta) of the ions under study and to uniaxial anisotropy. The possibility of using this pseudodipole interaction to explain the magnetic properties of cuprates is discussed. (C) 1998 American Institute of Physics.