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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Institution: | 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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