Europhys. Lett, 47 (1), pp. 116-121 (1999)
Anisotropic superexchange of a Cu-O-Cu bond
V. Yu. Yushankhai 1 and R. Hayn 2
1 Joint Institute for Nuclear Research - 141980 Dubna, Moscow
2 Institute for Theoretical Physics, TU Dresden - D-01062 Dresden, Germany
(received 2 February 1999; accepted 29 April 1999)
PACS. 75.30Gw - Magnetic anisotropy.
PACS. 74.72Jt - Other cuprates.
PACS. 71.70Ej - Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect.
The magnetic anisotropy of a rectangular Cu-O-Cu bond is investigated in second order of the spin-orbit interaction. Such a bond is characteristic for cuprates having edge sharing chains, and exists also in the plane or in ladder compounds. For a ferromagnetic coupling between the copper spins an easy axis is found perpendicular to the copper oxygen plaquettes in agreement with the experimental spin structure of . In addition, a pseudodipolar interaction is derived. Its estimation in the case of the plane (which is present for instance in or ) gives a value which is, however, two orders of magnitude smaller than the usual dipole-dipole interaction.
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