Regensburg 2010 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 41: CE: Low-dimensional Systems - Models 2
TT 41.3: Talk
Friday, March 26, 2010, 10:45–11:00, H21
Frustrated local moment models for Fe-pnictide magnetism — •Burkhard Schmidt, Mohammad Siahatgar, and Peter Thalmeier — Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden
The low energy spin excitations of the Fe pnictide parent compounds have been determined by inelastic neutron scattering and interpreted within the local moment J1a,b-J2 Heisenberg model with orthorhombic symmetry. This has led to alternative exchange models that strongly differ in the size of anisotropy. Although the compounds are itinerant the localised spin model can explain basic features of the excitations. The inherent frustration of this model leads to quantum fluctuations and possible moment reduction. We investigate this question in detail using spin wave approximation and partly exact diagonalisation Lanczos calculations for finite clusters. We find that the orthorhombic anisotropy stabilizes the columnar AF phase and its moment. For the exchange models proposed from inelastic neutron scattering we can exclude a strong influcence of frustration on the moment size. We also investigate dependence of magnetisation and susceptibility on field and temperature.