Magnetism of low doped spin chains in Lax(Sr,Ca)14-xCu24O41.

Kroll, T., Klingeler, R., Geck, J., Büchner, B., Selke, W., Hücker, M., and Gukasov, A.
IFW Dresden, Theoretische Physik, RWTH Aachen, Brookhaven National Lab, Laboratoire Leon-Brillouin


We present magnetization data of Lax(Sr,Ca)14-xCu24O41 (x >=5) in high magnetic fields up to 16 Tesla. The data reflect the magnetic response of lightly doped CuO2 spin chains containing <= 10 % non--magnetic holes. Our data provide a strongly anisotropic phase diagram. We present and analyse, using Monte Carlo techniques, a two--dimensional Ising model with mobile holes, describing experimental findings qualitatively.