Eur. Phys. J. B 77, 47-55 (2010)
https://doi.org/10.1140/epjb/e2010-00249-4

Ferromagnetic phases in spin-Fermion systems

Department of Physics, University of Sofia, 1126 Sofia, Bulgaria

Corresponding author: ^a naoum@phys.uni-sofia.bg

Received: 13 April 2010
Revised: 11 June 2010
Published online: 11 August 2010

Abstract

Spin-Fermion systems which obtain their magnetic properties from a system of localized magnetic moments being coupled to conducting electrons are considered. The dynamical degrees of freedom are spin-s operators of localized spins and spin-1/2 Fermi operators of itinerant electrons. Renormalized spin-wave theory, which accounts for the magnon-magnon interaction, and its extension are developed to describe the two ferromagnetic phases in the system: low temperature phase 0 < T < T*, where all electrons contribute the ordered ferromagnetic moment, and high temperature phase T* < T < T_C, where only localized spins form magnetic moment. The magnetization as a function of temperature is calculated. The theoretical predictions are utilize to interpret the experimentally measured magnetization-temperature curves of UGe₂.