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Pierre-Éric Melchy

Geometric frustration: The case of triangular antiferromagnets

Published on 8 October 2010

Thesis presented October 08, 2010

This doctoral dissertation presents a thorough determination of the phase diagrams of classical Heisenberg triangular antiferromagnet (HTAF) and its anisotropic variants based on theoretical and numerical analysis (Monte Carlo). At finite-field HTAF exhibits a non-trivial interplay of discrete Z3 symmetry and continuous S1 symmetry. They are successively broken (discrete then continuous) with distinct features at low and high fields: in the latter case the ordering is along transverse direction; in the former case an intermediate collinear phase is stabilized before 120-degree structure is. Due to zero-field behavior, transition lines close at (T,h) = (0,0). Single-ion anisotropy is here considered. Easy-axis HTAF for moderate anisotropy strength 0 < d

statistical physics, frustrated magnetism, triangular antiferromagnet, over-relaxation

On-line thesis.