Abstract
In this work, we propose a method for calculating the free energy of anisotropic classical spin systems. We use a Hubbard-Stratonovich transformation to express the partition function of a generic bilinear superexchange Hamiltonian in terms of a functional integral over classical time-independent fields. As an example, we consider an anisotropic spin-exchange Hamiltonian on the cubic lattice as is found for compounds with strongly correlated electrons in multiorbital bands and subject to strong spin-orbit interaction. We calculate the contribution of Gaussian spin fluctuations to the free energy. While the mean-field solution of ordered states for such systems usually has full rotational symmetry, we show here that the fluctuations lead to a pinning of the spontaneous magnetization along some preferred direction of the lattice.
Original language | English (US) |
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Article number | 155131 |
Journal | Physical Review B - Condensed Matter and Materials Physics |
Volume | 92 |
Issue number | 15 |
DOIs | |
State | Published - Oct 19 2015 |
Bibliographical note
Publisher Copyright:© 2015 American Physical Society. ©2015 American Physical Society.