Berlin 2008 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 13: Correlated Electrons: Low-dimensional Systems - Materials 1
TT 13.4: Talk
Tuesday, February 26, 2008, 10:15–10:30, H 2053
KTi(SO4)2.H2O - a possible candidate for a new spin-Peirles system — •Deepa Kasinathan1, Goran Nilsen2, Henrik Ronnow2, Stefan-Ludwig Drechsler3, and Helge Rosner1 — 1MPI CPfS - Dresden, Germany — 2LQM-EPFL, Lausanne, Switzerland — 3IFW Dresden, Germany
Recently a large number of compounds belonging to the family of J1−J2 chain models with competing ferromagnetic (FM) and antiferromagnetic (AFM) interactions have been discovered. In most cases, FM-J1 and AFM-J2 is observed, leading to helical order with no spin gap (for frustration ratio α = J1/J2 > -0.25). Systems with both J1 and J2 being AFM causing a spin gap are rather rare. The thermodynamic data of the recently prepared KTi(SO4)2.H2O reveal that this system is a quasi 1D spin 1/2 chain compound with both J1 and J2 being AFM, and a frustration ratio α ≈ 0.29. Here we report the results of electronic structure calculations within the LSDA+U method along with tight-binding models. Our calculations confirm that both J1 and J2 are AFM. In contrast to the experiments we obtain a larger α, slightly depending on the choice of the Coulomb repulsion U. Therefore KTi(SO4)2.H2O might be a new candidate for a spin-Peirles ground state. A brief comparison with other systems belonging to the class of frustrated chain materials is given with respect to their position in the general phase diagram of the 1D J1−J2 model.