Regensburg 2004 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 32: Theoretische Modelierung von Materialien mit korrelierten Elektronen
TT 32.11: Vortrag
Freitag, 12. März 2004, 12:45–13:00, H18
Finite-temperature analysis of 2D spin frustrated Vanadium compounds — •Burkhard Schmidt1, Nic Shannon1,2, Karlo Penc3, and Peter Thalmeier1 — 1MPI für Chemische Physik fester Stoffe, 01187 Dresden, Germany — 2SPEC, CEA Saclay, Orme des Merisiers, F-91191 Gif sur Yvette CEDEX, France — 3Research Institute of Solid State Physics and Optics, H-1525 Budapest, P.O. Box 49, Hungary
We present an analysis of the finite-temperature properties of the J1-J2 Heisenberg model on a square-lattice based on the exact diagonalisation of 8, 16, and 20 site clusters. Our method provides a possibility to determine the exchange constants of recent experimental realisations of the model in a unique way. In particular, the two-dimensional compounds Li2VO(Si,Ge)O4 and Pb2VO(PO4)2 will be discussed.
We propose that diffuse neutron scattering can be used to resolve the inherent ambiguity in determining the ratio and sign of J1 and J2 from thermodynamic properties alone, and use a finite temperature Lanczos algorithm to make predictions for the relevant high temperature spin-spin correlation functions.
We investigate the crossover between the various magnetic and spin-liquid phases for both ferromagnetic and antiferromagnetic couplings J1 and J2. We also analyse the nonlinear magnetic susceptibility to resolve the ambiguity of the frustration ratio J2/J1.