Volume 83, Number 6, September 2008
Article Number 67003
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 08 September 2008
EPL, 83 (2008) 67003
DOI: 10.1209/0295-5075/83/67003

Doping evolution of itinerant magnetic fluctuations in Fe-based pnictides

M. M. Korshunov1, 2 and I. Eremin1, 3

1   Max-Planck-Institut für Physik Komplexer Systeme - 01187 Dresden, Germany, EU
2   L.V. Kirensky Institute of Physics, Siberian Branch of Russian Academy of Sciences - 660036 Krasnoyarsk, Russia
3   Institute für Mathematische und Theoretische Physik, TU-Braunschweig - 38106 Braunschweig, Germany, EU

received 20 May 2008; accepted in final form 24 July 2008; published September 2008
published online 8 September 2008

Employing the four-band tight-binding model, we study theoretically the doping dependence of the spin response in the normal state of novel Fe-based pnictide superconductors. We show that the commensurate spin density wave (SDW) transition that arises due to interband scattering between the hole $\alpha $-pockets and the electron $\beta $-pockets disappears already at the doping concentration x $\approx$ 0.04 reflecting the evolution of the Fermi surfaces. Correspondingly, with further increase of the doping the antiferromagnetic fluctuations are suppressed for x > 0.1 and the imaginary part of the spin susceptibility at antiferromagnetic wave vector becomes nearly temperature independent. At the same time, we observe that the uniform susceptibility deviates from the Pauli-like behavior and is increasing with increasing temperature reflecting the activation processes for the $\alpha $-Fermi surfaces up to temperatures of about T = 800 K. With increase of the doping the absolute value of the uniform susceptibility lowers and its temperature dependence changes. In particular, it is a constant at low temperatures and then decreases with increasing temperature. We discuss our results in a context of recent experimental data.

74.20.-z - Theories and models of superconducting state.
74.25.Ha - Magnetic properties.
75.30.Fv - Spin-density waves.

© EPLA 2008