Spin-fluctuation theory beyond Gaussian approximation
Strongly Correlated Electrons
2010-04-27 v1 Materials Science
Mathematical Physics
math.MP
Abstract
A characteristic feature of the Gaussian approximation in the functional-integral approach to the spin-fluctuation theory is the jump phase transition to the paramagnetic state. We eliminate the jump and obtain a continuous second-order phase transition by taking into account high-order terms in the expansion of the free energy in powers of the fluctuating exchange field. The third-order term of the free energy renormalizes the mean field, and fourth-order term, responsible for the interaction of the fluctuations, renormalizes the spin susceptibility. The extended theory is applied to the calculation of magnetic properties of Fe-Ni Invar.
Keywords
Cite
@article{arxiv.1004.4278,
title = {Spin-fluctuation theory beyond Gaussian approximation},
author = {N. B. Melnikov and B. I. Reser and V. I. Grebennikov},
journal= {arXiv preprint arXiv:1004.4278},
year = {2010}
}
Comments
20 pages, 4 figures