Exact diagonalization studies of doped Heisenberg spin rings

Motivated by magnetization studies of the “telephone number compound” Sr14Cu24O41 we investigate Heisenberg spin rings containing non-magnetic sites (holes) by means of complete numerical diagonalization of a Heisenberg Hamiltonian that depends parametrically on hole positions. A comparison with experimental magnetization data reveals rather accurate information about the screened electrostatic interaction between the charged holes on the ring which appears to be astonishingly strong.