Vortex glass line and vortex liquid resistivity in doped BaFe2As2 single crystals

TL;DR

This study investigates the vortex glass transition and resistivity in doped BaFe2As2 single crystals, revealing how different dopants influence vortex behavior and pinning, with implications for superconductor performance.

Contribution

It provides a detailed analysis of vortex glass lines and resistivity scaling in doped BaFe2As2, highlighting the effects of magnetic and non-magnetic dopants on vortex states.

Findings

Non-magnetic K doping yields a high vortex glass line close to Hc2.

Magnetic Ni and Co doping result in a lower vortex glass line farther from Hc2.

Disorder type influences vortex pinning strength and glass state stability.

Abstract

The vortex liquid-to-glass transition has been studied in Ba0.72K0.28Fe2As2, Ba0.9Co0.1Fe2As2, and Ba(Fe0.45Ni0.05)2As2 single crystal with superconducting transition temperature, Tc = 31.7, 17.3, and 18 K, respectively, by magnetoresistance measurements. For temperatures below Tc, the resistivity curves were measured in magnetic fields within the range of 0 \leq B \leq 13 T, and the pinning potential was scaled according to a modified model for vortex liquid resistivity. Good scaling of the resistivity {\rho}(B, T) and the effective pinning energy U0(B,T) was obtained with the critical exponents s and B0. The vortex state is three-dimensional at temperatures lower than a characteristic temperature T*. The vortex phase diagram was determined based on the evolution of the vortex-glass transition temperature Tg with magnetic field and the upper critical field, Hc2. We found that non-magnetic K doping results in a high glass line close to the Hc2, while magnetic Ni and Co doping cause a low glass line which is far away from the Hc2. Our results suggest that non-magnetic induced disorder is more favourable for enhancement of pinning strength compared to magnetic induced disorder. Our results show that the pinning potential is responsible for the difference in the glass states.