Abstract:
The two-layer square lattice quantum antiferromagnet with spins 12 shows a zero-field magnetic order-disorder transition at a critical ratio of the inter-plane to intra-plane couplings. Adding a uniform magnetic field tunes the system to canted antiferromagnetism and eventually to a fully polarized state; similar behavior occurs for ferromagnetic intra-plane coupling. Based on a bond operator spin representation, we propose an approximate ground state wavefunction which consistently covers all phases by means of a unitary transformation. The excitations can be efficiently described as independent bosons; in the antiferromagnetic phase these reduce to the well-known spin waves, whereas they describe gapped spin-1 excitations in the singlet phase. We compute the spectra of these excitations as well as the magnetizations throughout the whole phase diagram.
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Received 23 April 2001
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Sommer, T., Vojta, M. & Becker, K. Magnetic properties and spin waves of bilayer magnets in a uniform field. Eur. Phys. J. B 23, 329–339 (2001). https://doi.org/10.1007/s100510170052
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DOI: https://doi.org/10.1007/s100510170052