Ca2Y2Cu5O10: the first frustrated quasi-1D ferromagnet close to criticality

TL;DR

This paper reports the discovery of Ca2Y2Cu5O10 as the first frustrated quasi-one-dimensional ferromagnet near criticality, with detailed exchange interactions and magnetic excitation properties studied via neutron scattering.

Contribution

It provides the first detailed characterization of Ca2Y2Cu5O10's magnetic interactions and proximity to the critical point in the J1-J2 chain model.

Findings

Exchange interactions J1 ≈ -170 K, J2 ≈ 32 K.

System is close to the critical ratio α=J2/J1≈0.19.

High-energy excitation intensities show strong temperature dependence.

Abstract

Ca2Y2Cu5O10 is build up from edge-shared CuO4 plaquettes forming spin chains. From inelastic neutron scattering data we extract an in-chain nearest neighbor exchange J1 approximately -170 K and the frustrating next neighbor J2 approximately 32 K interactions, both significantly larger than previous estimates. The ratio alpha= J2/J1 approximately 0.19 places the system very close to the critical point alpha_c=0.25 of the J1-J2 chain, but in the ferromagnetic regime. We establish that the vicinity to criticality only marginally affects the dispersion and coherence of the elementary spin-wave-like magnetic excitations, but instead results in a dramatic T-dependence of high-energy Zhang-Rice singlet excitation intensities.