Magnetic coupling in the weak ferromagnet CuF2

CuF2 is known to be an antiferromagnetic compound with a weak ferromagnetis m due to the anisotropy of its monoclinic unit cell (Dzialoshinsky-Moriya m echanism). We investigate the magnetic ordering of this compound by means o f ab initio periodic unrestricted Hartree-Fock calculations and by cluster calculations which employ state-of-the-art configuration interaction expans ions and modern density functional theory techniques. The combined use of p eriodic and cluster models permits us to firmly establish that the antiferr omagnetic order arises from the coupling of one-dimensional subunits which themselves exhibit a very small ferromagnetic coupling between Cu neighbor cations. This magnetic order could be anticipated from the close correspond ence between CuF2 and rutile crystal structures. [S0163-1829(99)15301-3].