High-field Electron Spin Resonance of Cu_{1-x}Zn_{x}GeO_{3}

TL;DR

This study investigates high-field electron spin resonance in Cu_{1-x}Zn_{x}GeO_{3} powders, revealing impurity-induced states within the Spin Peierls gap and a novel quenching phenomenon at phase boundaries.

Contribution

It provides the first experimental evidence linking impurity-induced states to ESR spectra and observes a new quenching effect across phase transitions in doped CuGeO3.

Findings

Resonance positions depend on Zn concentration, frequency, and temperature.

States inside the Spin Peierls gap are associated with impurity-induced 'loose' spins.

Quenching of ESR signal occurs at the Dimerized to Incommensurate phase boundary.

Abstract

High-Field Electron Spin Resonance measurements were made on powder samples of Cu_{1-x}Zn_{x}GeO_{3} (x=0.00, 0.01, 0.02, 0.03 and 0.05) at different frequencies (95, 110, 190, 220, 330 and 440 GHz) at low temperatures. The spectra of the doped samples show resonances whose positions are dependent on Zn concentration, frequency and temperature. The analysis of intensity variation of these lines with temperature allows us to identify them as originating in transitions within states situated inside the Spin Peierls gap. A qualitative explanation of the details of the spectra is possible if we assume that these states in the gap are associated with "loose" spins created near the Zn impurities, as recently theoreticaly predicted. A new phenomenon of quenching of the ESR signal across the Dimerized to Incommensurate phase-boundary is observed.