Magnon heat transport and magnon-hole scattering in one and two dimensions spin systems
The magnon thermal conductivity k_mag of the low dimensional quantum spin systems La2CuO4 and (Sr,Ca)14Cu24O41 with a focus on magnon hole scattering and its relevance for the magnetic heat transport has been investigated experimentally. In the two dimensional Heisenberg antiferromagnet La2CuO4 already slight hole doping (~1 %) almost completely suppresses k_mag. Comparison with k_mag of Zn-doped La2CuO4 reveals that magnon-hole scattering is even stronger than cattering on static magnetic defects. In (Sr,Ca)14Cu24O41 a strong doping and temperature dependence of k_mag is present at low Ca-doping levels ( x £ 5). Here a unique relation between heat transport and charge ordering in the ladder subunits of the material has been shown. In the charge ordered state at low temperatures magnon-hole scattering is completely unimportant, while it becomes strong at high temperatures where in strength it is comparable with scattering of magnons on static magnetic defects induced by Zn-doping. At high Ca-doping (x ³ 5) the doping dependence of k_mag is only weak. However, an anisotropic suppression of the phononic thermal conductivity at low temperatures indicates a new doping-induced one dimensional scattering process of phonons.
info:eu-repo/classification/ddc/530, Cuprate, Quantenspinsystem, Niederdimensionales System, Wärmeleitfähigkeit, Magnon, Physik
Networked Digital Library of Theses and Dissertations
Publikationsserver der RWTH Aachen University