Quantum spin model of a cubic ferromagnet in a magnetic field |
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Authors: | M. Dudzinski J. Sznajd J. Zittartz |
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Affiliation: | Institut für Theoretische Physik, Universit?t zu K?ln, 50937 K?ln, Germany, DE Institute for Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw 2, Poland, DE
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Abstract: | The zero temperature phase diagram of a one-dimensional ferromagnet with cubic single ion anisotropy in an external magnetic field is studied. The mean-field approximation and the density-matrix renormalization group method are applied. Two phases at finite magnetic fields are identified: a canted phase with spontaneously broken symmetry and a phase with magnetization along the magnetic field. Both methods predict that the canted phase exists even for the single-ion anisotropy strong enough to destroy the magnetic order at zero magnetic field. In contrast to the mean-field theory, the density-matrix renormalization group predicts a reentrant behavior for the model. The character of the phase transition at finite magnetic field has also been considered and the critical index has been found. Received 9 May 2000 and Received in final form 5 July 2000 |
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Keywords: | PACS. 75.10.Dg Crystal-field theory and spin Hamiltonians - 75.10.Jm Quantized spin models - 75.30.Gw Magnetic anisotropy |
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