Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 33: Postersession Correlated Electrons: Metal Insulator Transition, Spin Systems and Itinerant Magnets
TT 33.19: Poster
Mittwoch, 25. März 2009, 14:00–18:00, P1A
Thermodynamics of a one-dimensional frustrated spin-1/2 Heisenberg ferromagnet — •Moritz Härtel1, Johannes Richter1, Dieter Ihle2, and Stefan-Ludwig Drechsler3 — 1ITP, OvG-Universität Magdeburg, D-39016 Magdeburg, Germany — 2ITP, Universität Leipzig — 3Leibniz-Institut IFW Dresden
The frustrated one-dimensional J1-J2 Heisenberg ferromagnet (J1=−1, J2>0) has attracted much attention due to recent experiments on edge-shared chain-cuprates, e.g. LiVCuO4 and Li2CuO2.
We use a second-order Green’s function technique and the full exact diagonalization of finite systems of up to N=22 lattice sites to calculate thermodynamic properties (correlations functions ⟨ S0Sn⟩, correlation length ξ, isothermal spin susceptibility χ, and specific heat CV). Although we restrict on the ferromagnetic ground state, i.e. J2<0.25, the frustration influences the thermodynamics substantially. We find that the critical indeces of the susceptibility and the correlation length are not changed by a finite frustration in absence of a magnetic field, i.e. χ=y0T−2 and ξ=x0T−1 at T→ 0. The coefficients y0 and x0 decrease linearly with increasing J2 and vanish at the critical point J2=0.25 due to the zero-temperature phase transition that is accompanied by a change in the critical behavior. In addition, we detect the existence of an additional low-temperature maximum in the specific heat when approaching the critical point. Including a weak magnetic field (h 0.07) this additional maximum exists already at J2=0 but gets more pronounced with increasing J2.