Observation of vortex structure in MgB$_2$ single crystals by Bitter decoration technique

TL;DR

This study visualizes superconducting vortices in MgB₂ single crystals using Bitter decoration, revealing vortex lattice structures and estimating the London penetration depth, advancing understanding of vortex behavior in this superconductor.

Contribution

It provides direct imaging of vortex structures in MgB₂ crystals and measures the London penetration depth, offering new insights into vortex arrangements in this material.

Findings

Triangular vortex lattice observed in real space

London penetration depth estimated at ~1900 Å at 6 K

Vortex imaging achieved in both pure and lightly Al-doped MgB₂

Abstract

We report the observation of superconducting vortices in pure and lightly Al doped MgB$_2$ single crystals. Low field experiments allow for the estimation of the London penetration depth, lambda ~ 1900 $\AA$ for T$\sim$6 K. Experiments in higher fields (e.g. 200 Oe) clearly show a triangular vortex lattice in both real space (13 $\mu$m by 13 $\mu$m Bitter decoration image of over 1000 vortices) and reciprocal space.