Direct measurement of the magnetic penetration depth by magnetic force microscopy

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 for a reference sample. Using a well-characterized Nb film as a reference, we determine the absolute value of lambda in a Ba(Fe0.92Co0.08)(2)As-2 single crystal and a MgB2 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.