Magnetic Resonance of the Intrinsic Defects of the Spin-Peierls Magnet CuGeO3

TL;DR

This study investigates the electron spin resonance (ESR) of pure CuGeO3 crystals at low temperatures, revealing defect-related spectral components linked to the spin-Peierls phase and domain boundaries.

Contribution

It identifies and analyzes magnetic defect signals in CuGeO3, distinguishing between different defect types and their magnetic resonance characteristics.

Findings

Splitting of ESR line below 5 K indicates defect states.

Identification of S=1/2 and S=1 defect signals.

Anomalous g-factor and power-dependent susceptibility of additional ESR line.

Abstract

ESR of the pure monocrystals of CuGeO3 is studied in the frequency range 9-75 GHz and in the temperature interval 1.2-25 K. The splitting of the ESR line into several spectral components is observed below 5 K, in the temperature range where the magnetic susceptibility is suppressed by the spin-Peierls dimerization. The analysis of the magnetic resonance signals allows one to separate the signals of the S=1/2- and S=1 defects of the spin-Peierls phase. The value of g-factor of these signals is close to that of the Cu-ion. The additional line of the magnetic resonance is characterized by an anomalous value of the g-factor and by the threshold-like increase of the microwave susceptibility when the microwave power is increasing. The ESR signals are supposingly attributed to two types of the planar magnetic defects, arising at the boundaries of the domains of the spin-Peierls state with the different values of the phase of the dimerization.