Investigation of fundamental and higher harmonic AC magnetic susceptibility of FeSe0.5Te0.5 Superconductor

TL;DR

This study investigates the complex harmonic AC magnetic susceptibility of FeSe0.5Te0.5 superconductor under various conditions, revealing vortex glass behavior and flux dynamics through harmonic analysis and susceptibility measurements.

Contribution

It provides a detailed analysis of harmonic susceptibilities and identifies vortex glass state in FeSe0.5Te0.5, advancing understanding of its flux dynamics and magnetic response.

Findings

Complex harmonic susceptibilities vary with external perturbations.

Negative and positive peaks in third harmonic susceptibility shift with frequency.

Sample exhibits vortex glass state characterized by collective flux creep.

Abstract

We present the complex harmonic magnetic susceptibilities of the FeSeTe polycrystalline superconducting sample. The ac magnetic susceptibility is measured as a function of various external perturbations such as temperature, the AC magnetic field amplitude, frequency, and the magnitude of DC bias field. The in phase and out of phase components of the fundamental and third harmonics of ac susceptibility are found to vary as a function of the AC drive field. The imaginary part of third harmonics shows two peaks as a function of frequency, one negative in magnitude and another is positive. The negative peak shifts towards the lower temperature and positive peak is shifted towards the higher temperature as we increase the frequency. To better understand the AC magnetic response under the influence of various perturbations, we have analyzed the polar plot of the complex ac susceptibility for both the harmonics. Our analysis suggests that the studied sample is in vortex glass state, characterized by a collective flux creep state within Beans model and the Kim Anderson model is ruled out.