Revisiting and modeling the magnetism of hole-doped CuO_2 spin chains in Sr{14-x}Ca_xCu_{24}O_{41}

TL;DR

This study investigates how Ca doping affects the magnetic properties of CuO_2 spin chains in Sr14-xCaxCu24O41, revealing complex changes in low-temperature magnetization not explained by simple models.

Contribution

The paper revisits the magnetism of hole-doped CuO_2 chains and proposes alternative explanations for observed magnetic susceptibility changes with Ca doping.

Findings

Magnetization varies strongly with Ca doping at low temperatures.

Quantum simulations fit well with an effective Heisenberg model for x=0.

Additional magnetic contributions appear for x>0 that challenge simple models.

Abstract

Magnetization measurements of Sr{14-x}Ca_xCu_{24}O_{41} with 0 <= x <=12 in magnetic fields up to 16 T show that the low-temperature magnetic response of the CuO_2 spin chains changes strongly upon Ca doping. For x=0 quantum statistical simulations yield that the temperature and field dependence of the magnetization can be well described by an effective Heisenberg model in which the ground state configuration is composed of spin dimers, trimers, and monomers. For x>0 a constant contribution to the low-temperature magnetic susceptibility is observed which cannot be explained in terms of simple chain models. Alternative scenarios are outlined.