Low density flux pinning in YBCO single crystals

TL;DR

This study investigates vortex dynamics and flux pinning in YBCO single crystals under Earth's magnetic field, estimating key parameters like pinning potential and critical current density through relaxation and magnetization measurements.

Contribution

It provides new insights into flux pinning mechanisms and effective pinning potentials in YBCO crystals at low magnetic fields, comparing different measurement techniques.

Findings

Estimated effective pinning potential U and its temperature dependence.

Determined critical current density Jc and other parameters like penetration field Hp.

Compared flux pinning behavior at Earth's magnetic field with higher field data.

Abstract

The Abricosov vortex and bundles dynamics was experimentally investigated in Earth's magnetic field range. Isothermal relaxation features in YBCO single crystal samples with strong pinning centers were studied for different sample-field orientation. The normalized relaxation rate S obtained allowed to estimate the effective pinning potential U in the bulk of the YBCO sample and its temperature dependence, as well as the critical current density Jc. A comparison between the data obtained and the results for similar measurements in significantly higher magnetic fields was performed. To compare different Jc measuring techniques magnetization loop M(H) measurements, were made. These measurements provide many important parameters of the sample under study (penetration field Hp, first critical field Hc1, etc.) that contain the geometrical configuration of the samples.