Analysis of magnetic response of critical state in second-generation high temperature superconductor YBa2Cu3Ox wire

Abstract

We have measured magnetic response of second-generation high temperature superconductor YBa2Cu3Ox wire in perpendicular ac field as a function of temperature. We compare complex ac susceptibility to the calculated susceptibility based on the model of Bean’s critical-state response in two-dimensional (2D) disk in perpendicular field and infinitely long cylinder in parallel field. We present a method of linking model and experimental susceptibility. Good agreement of experimental susceptibility with model susceptibility of 2D disk allows noncontact estimation of critical depinning current density and its temperature dependence.

dc and ac magnetic properties of thin-walled superconducting niobium cylinders

“…Low-T c superconductors were investigated a long time ago [1][2][3] and revealed an absorption maximum at the transition upon variation of temperature and dc magnetic field. The ac response of high-T c superconductors exhibits similar features [4][5][6]. However, the physical reasons for this behavior remain unclear.…”

“…The ac magnetic response contains essential information about the properties of superconductors. Peculiarities of the ac response of conventional and high-T c superconductors have been a matter of extensive research [1][2][3][4][5][6]. Low-T c superconductors were investigated a long time ago [1][2][3] and revealed an absorption maximum at the transition upon variation of temperature and dc magnetic field.…”

Contactless Estimation of Critical Current Density and Its Temperature Dependence Using Magnetic Measurements

“…The M (f ) and H(f ) are the Fourier transforms of m(t) and h(t), respectively. The model susceptibility is calculated in the same way from model magnetization curves [5]. We assume temperature dependence of the critical depinning current density…”

“…A signal proportional to the magnetic moment of the sample, m(t), and signal of the applied field h(t) (proportional to a supply current) are digitized and recorded on a hard disk. The complex ac susceptibility χ(f ) = M (f )/H(f ) is calculated in real time using discrete fast Fourier transform [5]. The M (f ) and H(f ) are the Fourier transforms of m(t) and h(t), respectively.…”

“…The model to 2D disk in perpendicular applied time varying field was worked out by Clem and Sanchez [4]. We have shown that this model correctly predicts the response of the YBCO wire and allows estimate in a contactless way the critical current density and its temper-ature dependence [5]. In this paper we reanalyze earlier measurements on Nb film [6] using a method first applied to the YBCO wire and we compare the results.…”