Eur. Phys. J. D 52, 167-170 (2009)
https://doi.org/10.1140/epjd/e2008-00243-7

Functional-integral study of spin fluctuations in small Fe clusters

¹ Facultad de Ciencias Físico Matemáticas, Universidad Autónoma de Coahuila, CU Camporredondo, 25000 Saltillo, Mexico
² Instituto de Física, Universidad Autónoma de San Luis Potosí, 78000 San Luis Potosí, Mexico
³ Institut für Theoretische Physik, Universität Kassel, 34132 Kassel, Germany

Corresponding author: ^a pastor@uni-kassel.de

Received: 19 September 2008
Published online: 24 January 2009

Abstract

Finite temperature magnetic properties of small Fe_N clusters (N ≤6) are determined in the framework of a spin-fluctuation itinerant-electron theory based on a functional integral formulation of the canonical partition function and derived statistical averages. The free energy associated to each configuration of the exchange fields throughout the cluster are calculated by using Haydock-Heine-Kellys recursion method. The statistical averages of physical interest are obtained by performing parallel-tempering Monte Carlo simulations. Representative results are discussed for the average magnetization per atom as a function of temperature. The interplay between local environment and magnetization curves is analyzed by considering the low-temperature limit of the local spin-fluctuations energies ΔF_l(ξ) at different atoms l. The electronic calculations are contrasted with the predictions of simple of phenomenological Heisenberg-like models.