Effects of hole-doping on the magnetic ground state and excitations in the edge-sharing CuO$_2$ chains of Ca$_{2+x}$Y$_{2-x}$Cu$_5$O$_{10}$

TL;DR

This study investigates how hole doping affects magnetic excitations in CuO chains of Ca$_{2+x}$Y$_{2-x}$Cu$_5$O$_{10}$, revealing increased broadening and softening of excitations with doping and temperature, and linking spin-glass behavior to hole-induced clusters.

Contribution

It provides a systematic analysis of temperature and doping effects on magnetic excitations in edge-sharing CuO chains, highlighting the impact of hole doping on broadening and magnetic interactions.

Findings

Magnetic excitations soften and broaden with doping and temperature.

Hole doping significantly enhances excitation broadening along the chains.

Spin-glass phase arises from antiferromagnetic clusters caused by hole disproportionation.

Abstract

Neutron scattering experiments were performed on the undoped and hole-doped Ca$_{2+x}$Y$_{2-x}$Cu$_5$O$_{10}$, which consists of ferromagnetic edge-sharing CuO$_2$ chains. It was previously reported that in the undoped Ca$_2$Y$_2$Cu$_5$O$_{10}$ there is an anomalous broadening of spin-wave excitations along the chain, which is caused mainly by the antiferromagnetic interchain interactions [Matsuda $et$ $al.$, Phys. Rev. B 63, 180403(R) (2001)]. A systematic study of temperature and hole concentration dependencies of the magnetic excitations shows that the magnetic excitations are softened and broadened with increasing temperature or doping holes irrespective of $Q$ direction. The broadening is larger at higher $Q$. A characteristic feature is that hole-doping is much more effective to broaden the excitations along the chain. It is also suggested that the intrachain interaction does not change so much with increasing temperature or doping although the anisotropic interaction and the interchain interaction are reduced. In the spin-glass phase ($x$=1.5) and nearly disordered phase ($x$=1.67) the magnetic excitations are much broadened in energy and $Q$. It is suggested that the spin-glass phase originates from the antiferromagnetic clusters, which are caused by the hole disproportionation.