Direct measurement of the magnetic penetration depth by magnetic force microscopy

TL;DR

This paper introduces a magnetic force microscopy method for directly measuring the magnetic penetration depth in superconductors, providing a simple, robust, and reference-based approach applicable to thin films and single crystals.

Contribution

The authors develop a new experimental technique that measures the absolute magnetic penetration depth without complex tip modeling, using reference samples for comparison.

Findings

Measured λ in a Ba(Fe,Co)2As2 crystal using the method.

Determined λ in MgB2 thin film.

Apparatus allows simultaneous loading and measurement of multiple samples.

Abstract

We present an experimental approach using magnetic force microscopy for measurements of the absolute value of the magnetic penetration depth $\lambda$ in superconductors. $\lambda$ is obtained in a simple and robust way without introducing any tip modeling procedure via direct comparison of the Meissner response curves for a material of interest to those measured on a reference sample. Using a well-characterized Nb film as a reference, we determine the absolute value of $\lambda$ in a Ba(Fe$_{0.92}$Co$_{0.08}$)$_{2}$As$_{2}$ single crystal and a MgB$_2$ thin film through a comparative experiment. Our apparatus features simultaneous loading of multiple samples, and allows straightforward measurement of the absolute value of $\lambda$ in superconducting thin film or single crystal samples.