Electron Spin Resonance of defects in the Haldane System Y(2)BaNiO(5)

TL;DR

This paper models and calculates the electron paramagnetic resonance spectra of a Haldane system, successfully matching experimental data and revealing end-chain spin states using DMRG techniques.

Contribution

It provides a detailed theoretical calculation of EPR spectra for Y(2)BaNiO(5), incorporating experimental parameters and identifying end-chain S=1/2 states.

Findings

Quantitative match between calculated and observed EPR spectra.

Identification of end-chain S=1/2 states as main spectral feature.

Model accurately reproduces spectral structure at low temperatures.

Abstract

We calculate the electron paramagnetic resonance (EPR) spectra of the antiferromagnetic spin-1 chain compound Y(2)BaNi(1-x)Mg(x)O(5) for different values of x and temperature T much lower than the Haldane gap (~100K). The low-energy spectrum of an anisotropic Heisenberg Hamiltonian, with all parameters determined from experiment, has been solved using DMRG. The observed EPR spectra are quantitatively reproduced by this model. The presence of end-chain S=1/2 states is clearly observed as the main peak in the spectrum and the remaining structure is completely understood.