Ising magnets with mobile defects.

Selke, W.
Institut für Theoretische Physik, Technische Hochschule Aachen,
D-52056 Aachen, Germany

V. L. Pokrovsky
Department of Physics, Texas A & M, College Station, USA

Büchner, B., Kroll T.
Institut für Experimentalphysik, Technische Hochschule Aachen,
D-52056 Aachen, Germany


Motivated by recent experiments on cuprates with low-dimensional magnetic interactions, a new class of two-dimensional Ising models with short-range interactions and mobile defects is introduced an studied. The non-magnetic defects form lines, which, as temperature increases, first meander and then become unstable. Using Monte Carlo simulations and analytical low- and high-temperature considerations, the instability of the defect stripes is monitored for various microscopic and thermodynamic quantities in detail for a minimal model, assuming some of the couplings to be indefinitely strong. The robustness of the findings against weakening the interactions is discussed as well.