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MA: Magnetismus

MA 5: Spinstrukturen und magnetische Phasenüberg
änge

MA 5.7: Talk

Friday, March 4, 2005, 12:00–12:15, TU EMH225

Magnetism of weakly doped spin chains in La₅Ca₉Cu₂₄O₄₁ — •R. Leidl¹, R. Klingeler², B. Büchner², W. Selke¹, and M. Holtschneider¹ — ¹Institut für Theoretische Physik, RWTH Aachen, 52056 Aachen, Germany — ²IFW Dresden, PF 270116, 01171 Dresden, Germany

Recent experiments revealed rather surprising magnetic properties of weakly hole doped spin chains in the “telephone number” compound La₅Ca₉Cu₂₄O₄₁. In particular, at low magnetic fields a small anomaly, indicating a phase transition, in the susceptibility curves (and other quantities) is observed, followed by a rather broad maximum at higher fields where one would usually expect a spin-flop transition. In an effort to (partially) understand these observations we study a classical anisotropic Heisenberg antiferromagnet with spinless holes, using mainly Monte Carlo simulations. We show that a broad maximum in the susceptibility can be caused by a disorder effect, originating in the influence of randomly distributed, immobile holes on the spin-flop transition.