The origin of paramagnetic magnetization in field-cooled YBa2Cu3O7 films

TL;DR

This study investigates the paramagnetic Meissner effect in YBa2Cu3O7 films, demonstrating that vortex nucleation and redistribution during field cooling cause the effect, aligning experimental results with a theoretical model.

Contribution

It provides experimental validation that vortex behavior explains the paramagnetic response in high-temperature superconductor films, confirming the theoretical model by Koshelev and Larkin.

Findings

Paramagnetic signal observed in YBa2Cu3O7 films.

Experimental data aligns with the vortex nucleation model.

Vortex distribution is highly sensitive to film and measurement conditions.

Abstract

Temperature dependences of the magnetic moment have been measured in YBa_2Cu_3O_{7-\delta} thin films over a wide magnetic field range (5 <= H <= 10^4 Oe). In these films a paramagnetic signal known as the paramagnetic Meissner effect has been observed. The experimental data in the films, which have strong pinning and high critical current densities (J_c ~ 2 \times 10^6 A/cm^2 at 77 K), are quantitatively shown to be highly consistent with the theoretical model proposed by Koshelev and Larkin [Phys. Rev. B 52, 13559 (1995)]. This finding indicates that the origin of the paramagnetic effect is ultimately associated with nucleation and inhomogeneous spatial redistribution of magnetic vortices in a sample which is cooled down in a magnetic field. It is also shown that the distribution of vortices is extremely sensitive to the interplay of film properties and the real experimental conditions of the measurements.