Quasi-two-dimensional hole ordering and dimerized state in the CuO2-chain layers in Sr14Cu24O41

TL;DR

This study uses neutron scattering to reveal quasi-two-dimensional hole ordering and dimerized magnetic states in Sr14Cu24O41, highlighting the magnetic excitation spectrum and effects of Ca substitution.

Contribution

It provides the first detailed characterization of magnetic excitations and hole ordering in Sr14Cu24O41, including the effects of Ca doping on these properties.

Findings

Magnetic excitations have two weakly dispersive branches.

The dispersion can be modeled with a random phase approximation.

Ca substitution affects hole and dimer ordering.

Abstract

Neutron scattering experiments have been performed on Sr$_{14}$Cu$_{24}$O$_{41}$ which consists of both chains and ladders of copper ions. We observed that the magnetic excitations from the CuO$_2$ chain have two branches and that both branches are weakly dispersive along the $a$ and $c$ axes. The $\omega$-$Q$ dispersion relation as well as the intensities can be reasonably described by a random phase approximation with intradimer coupling between next-nearest-neighbor copper spins $J$=11 meV, interdimer coupling along the c axis $J_c$=0.75 meV, and interdimer coupling along the a axis $J_a$=0.75 meV. The dimer configuration indicates a quasi-two-dimensional hole ordering, resulting in an ordering of magnetic Cu$^{2+}$ with spin-1/2 and nonmagnetic Cu, which forms the Zhang-Rice singlet. We have also studied the effect of Ca substitution for Sr on the dimer and the hole ordering.