Magnetic susceptibility and short-range order in iron pnictides: Anisotropic J1-J2 Heisenberg model
Joint Institute for Nuclear Research, 141980
2 Institut für Theoretische Physik, Universität Leipzig, 04109 Leipzig, Germany
Received: 7 March 2014
Published online: 15 May 2014
A spin-rotation-invariant Green-function theory for the dynamic spin susceptibility in the anisotropic non-frustrated J1-J2 model for the iron pnictides AFe2As2 (A = Ca, Sr, Ba) is presented. The two-spin correlation functions, the spin-excitation spectrum, and the staggered magnetization are calculated self-consistently as functions of temperature and spin. The temperature dependence of the magnetic (uniform static) susceptibility, in particular the linear increase with T in a wide temperature region that is in good quantitative agreement with experiments, is ascribed to a strong in-plane antiferromagnetic short-range order. The values of the Néel temperature resulting from the localized spin model with realistic out-of-plane couplings are found to be much higher than the measured values. From this an extension of the model by including itinerant degrees of freedom is suggested.
Key words: Solid State and Materials
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2014