Dresden 2011 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 18: CE: Low-dimensional Systems - Materials 1

TT 18.3: Vortrag

Montag, 14. März 2011, 19:00–19:15, HSZ 201

Ferromagnetic versus helical order in edge sharing CuO₂ chains - a computational study — •Helge Rosner¹, Ulrike Nitzsche², Roman Kuzian², and Stefan-Ludwig Drechsler² — ¹MPI CPfS Dresden — ²IFW Dresden

The magnetic ground state of edge sharing CuO₂ spin 1/2 Heisenberg chains with ferromagnetic nearest neighbor exchange J₁ and antiferromagnetic second neighbor exchange J₂ depends delicately on structural details of the crystal structure, like Cu-O-Cu bond angles, Cu-O distances and the position of the cations. Without taking into account a renormalization by the interchain coupling, a critical ratio α=−J₂/J₁=1/4 separates a ferromagnetic from a helical ground state (FM for α < 1/4, helical for α > 1/4). Here, we present a density functional based band structure study that investigates the different influences of various structural parameters for Li₂CuO₂ as example compound. We find that the ferromagnetic and antiferromagnetic contributions develop rather differently for the same structural changes. Therefore, the key parameter α for the ground state is especially sensitive to small structural changes that might be induced by temperature or pressure variation.