Eur. Phys. J. B 17, 575-579 (2000)
https://doi.org/10.1007/s100510070094

Quantum spin model of a cubic ferromagnet in a magnetic field

¹ Institut für Theoretische Physik, Universität zu Köln, 50937 Köln, Germany
² Institute for Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wroclaw 2, Poland

Received: 9 May 2000
Revised: 5 July 2000
Published online: 15 October 2000

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.