Design and fabrication of cryogenic probe for penetration depth measurements down to 1.8 K

Abstract

We describe the design and fabrication of a cryogenic probe for measurements of magnetic penetration depth (λ) down to 1.8 K. Penetration depth provides fundamental information about the nature of superconductivity and sets the length scale for vortex dynamics. Our probe employs the single coil self inductance technique at radio frequencies, in which the coil configuration along with the temperature stabilized tunnel diode oscillator enable the measurement of λ for thin film samples. There is also a provision for studying modulation of λ in the presence of small magnetic fields generated from an inbuilt coaxial superconducting coil. We present the performance of this probe in controlled sustenance of temperatures below 4.2 K and attainment of a signal-to-noise ratio of ~10⁵,while measuring superconducting transition of a foil of indium.