On the parameters of intermediate state structure in high pure type I superconductors at external magnetic field

TL;DR

This study investigates the intermediate state structure in high purity type I superconductors, specifically Gallium, under external magnetic fields using ultrasonic attenuation, revealing effects of magnetic field inhomogeneities and partial agreement with Landau theory.

Contribution

It provides experimental insights into the intermediate state structure of high purity Gallium superconductors and examines the influence of magnetic field inhomogeneities using ultrasonic methods.

Findings

Edge inhomogeneities affect the intermediate state structure.

Superconducting plane screens help approach equilibrium state.

Partial qualitative agreement with Landau theory.

Abstract

The geometric structure of an intermediate state in the high pure Gallium single crys-tal at the external magnetic field Hext at the temperature T=0.4 K is researched, using the longi-tudinal ultrasonic signal attenuation method at the ultrasonic signal frequency of 30 MHz. It is experimentally shown that the edge inhomogeneities of the magnetic field distribution have an influence on the structure of an intermediate state in the cylindrical superconductor samples at the transverse orientation of external magnetic field Hext. It is shown that the use of the super-conducting plane screens of NbZr permits an approach to the equilibrium intermediate state structure of an infinite cylinder as confirmed by an experimental dependence of the normal metal layer thickness aN on the magnitude of external magnetic field aN(Hext) in the high pure Ga single crystal at an application of the longitudinal ultrasonic signal with the frequency of 30 MHz at the temperature T=0.4 K. The experimentally obtained characteristic parameters of an intermediate state structure in the high pure type I superconductor at the external magnetic field Hext have a partial qualitative agreement with the Landau theory results.