Neutron inelastic scattering investigation of the magnetic excitations in Cu_2Te_2O_5X_2 (X=Br, Cl)

TL;DR

This study uses neutron inelastic scattering to explore magnetic excitations in Cu_2Te_2O_5X_2 (X=Br, Cl), revealing dispersive magnetic modes linked to 3D incommensurate order and temperature-dependent behaviors.

Contribution

It provides new insights into the magnetic excitation spectra and temperature evolution in Cu_2Te_2O_5X_2 compounds, highlighting differences between chloride and bromide variants.

Findings

Magnetic excitations with dispersive components observed in both compounds.

Excitations soften near the magnetic transition temperature in Cu_2Te_2O_5Cl_2.

Presence of magnetic excitations above transition temperature in Cu_2Te_2O_5Br_2.

Abstract

Neutron inelastic scattering investigations have been performed on the spin tetrahedral system Cu_2Te_2O_5X_2 (X = Cl, Br). We report the observation of magnetic excitations with a dispersive component in both compounds, associated with the 3D incommensurate magnetic order that develops below $T^{Cl}_{N}$=18.2 K and $T^{Br}_{N}$=11.4 K. The excitation in Cu_2Te_2O_5Cl_2 softens as the temperature approaches $T^{Cl}_{N}$, leaving diffuse quasi-elastic scattering above the transition temperature. In the bromide, the excitations are present well above $T^{Br}_{N}$, which might be attributed to the presence of a degree of low dimensional correlations above $T^{Br}_{N}$ in this compound.