Magnetic relaxation in pulse-magnetized high-temperature superconductors

TL;DR

This study investigates magnetic flux relaxation in pulse-magnetized high-temperature superconductors at 78K, revealing complex behavior influenced by magnetization strength and temperature distribution.

Contribution

It provides new insights into the non-monotonous relaxation rate behavior and its dependence on external magnetic field and temperature distribution during pulse magnetization.

Findings

Logarithmic increase of magnetic flux density with negative relaxation rate at weak magnetization.

Relaxation rate changes sign and exhibits a maximum as external magnetic field increases.

Non-homogeneous temperature distribution explains the non-monotonous relaxation behavior.

Abstract

A magnetic field relaxation at the center of a pulse-magnetized single-domain Y-Ba-Cu-O superconductor at 78K has been studied. In case of a weak magnetization, the magnetic flux density increases logarithmically and normalized relaxation rate defined as S=-d(lnB)/d(lnt) is negative (S=-0.037). When an external magnetic field magnitude increases, the relaxation rate first decreases in absolute value, then changes sign (becomes positive, S>0) and after reaching some maximum finally reduces to a very small value. Non-monotonous dependence of S vs Ha is explained by a non-homogeneous local temperature distribution during a pulse magnetization.