Doping dependent Irreversible Magnetic Properties of Ba(Fe1-xCox)2As2 Single Crystals

TL;DR

This study investigates how doping levels affect the irreversible magnetic properties of Ba(Fe1-xCox)2As2 single crystals, revealing complex vortex dynamics and similarities to cuprate superconductors.

Contribution

It provides a comprehensive analysis of doping-dependent magnetic behavior and vortex dynamics in Ba(Fe1-xCox)2As2, highlighting similarities to high-Tc cuprates.

Findings

Doping influences the second peak field Hp and vortex behavior.

Magnetic relaxation is fast and follows a logarithmic time dependence.

Vortex physics resembles that of high-Tc cuprates more than conventional superconductors.

Abstract

We discuss the irreversible magnetic properties of self-flux grown Ba(Fe1-xCox)2As2 single crystals for a wide range of concentrations covering the whole phase diagram from the underdoped to the overdoped regime, x=0.038, 0.047, 0.058, 0.071, 0.074, 0.10, 0.106 and 0.118. Samples were characterized by a magneto-optical method and show excellent spatial uniformity of the superconducting state. The overall behavior closely follows classical Bean model of the critical state. The field-dependent magnetization exhibits second peak at a temperature and doping - dependent magnetic field, Hp. The evolution of this fishtail feature with doping is discussed. Magnetic relaxation is time-logarithmic and unusually fast. Similar to cuprates, there is an apparent crossover from collective elastic to plastic flux creep above Hp. At high fields, the field dependence of the relaxation rate becomes doping independent. We discuss our results in the framework of the weak collective pinning and show that vortex physics in iron-based pnictide crystals is much closer to high-Tc cuprates than to conventional s-wave (including MgB2) superconductors.