The Effect of Spin-Peierls Instability Suppression in Nanometer-Scale-Sized CuGeO3 Crystals

Resumo

In this work, we study the influence of size effects on magnetic properties of quasi-one-dimensional spin-Peierls magnet CuGeO₃. It was found that the reduction of the crystallite’s size to nanometer scale (~300 × 30 nm) leads to full suppression of spin-Peierls transition, which takes place in the bulk material at \(T\approx 14\) K. Combined analysis of electron spin resonance (ESR) and magnetic susceptibility measurements allowed separating of the dynamic magnetization of Cu chains \(\chi _{ESR}\). Its temperature dependence is found to be typical for one-dimensional magnets with quantum critical (QC) behavior and is described by Curie–Weiss law \(\chi \sim \frac{1}{T+\Theta }\) at high temperatures, turning into power law asymptotic \(\chi \sim T^{-\alpha }\)\((\alpha <1)\) with temperature decrease. The data for two samples with different synthesis times (24 and 96 h) are analyzed in the framework of the QC behavior model. Although the values of magnetic parameters strongly depend on the synthesis time, the qualitative behavior is similar for both samples, which is shown by a comparative study of QC behavior of CuGeO₃ doped with 1 % of Fe. We argue that the reason for the observed behavior is the competition between the onset of the staggered magnetic field and dimerization effects.