An improved method for quantitative magneto-optical analysis of superconductors

Abstract

We report on the analysis method to extract quantitative local electrodynamics in superconductors by means of the magneto-optical technique. First of all, we discuss the calibration procedure to convert the local light intensity values into magnetic induction field distribution and start focusing on the role played by the generally disregarded magnetic induction components parallel to the indicator film plane (in-plane field effect). To account for the reliability of the whole technique, the method used to reconstruct the electrical current density distribution is reported, together with a numerical test example. The methodology is applied to measure local magnetic field and current distributions on a typical YBa 2 Cu 3 O 7−x good quality film. We show how the in-plane field influences the MO measurements, after which we present an algorithm to account for the in-plane field components. The meaningful impact of the correction on the experimental results is shown. Afterwards, we discuss some aspects about the electrodynamics of the superconducting sample.

Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields: Experiment and model

“…58,59 It is important to ensure that the contribution of the transverse field to the MO signal is negligible if the MOI technique is to be used effectively for crossed-field experiments. A detailed study 58 shows that the gray level values G plotted in a MO image can be expressed as a function of B z and B y as…”

Multifunctional La0.7Sr0.3MnO3-YBa2Cu3O7Heterostructures

“…Due to antagonism between ferromagnetism and superconductivity it is reasonable to expect that PE in F should be very short ranged. Surprisingly, some of the experiments [4] seem to be in contradiction with short- (15) -range nature of the PE in S/F structures. These models explain the long range PE by the formation of a strong triplet pairing amplitude component.…”

“…The polarization plane of the light is locally rotated by the indicator in dependence on the local perpendicular magnetic field component due to the Faraday effect. Then the light contrast of the frame acquired by the camera, after the analyzer, is proportional to the magnetic field distribution induced by the sample [15,16].…”

Magneto-Optics of Spontaneous and Field Induced Vortices in Twinned YBa2Cu3O7-δ/La1-xSrxMnO3Bilayers

“…The MO imaging of the magnetic distribution generated by flat materials is achieved by the use of a Bi-doped iron garnet film, with in-plane magnetization, as the MO indicator [15]. The magnetic imaging is performed in a reflection microscope equipped with Glan-Thompson polarizers, Hg arc lamp, and high resolution digital camera [16]. The indicator thickness and the finite distance from the magnetic source are the limiting factors for the spatial resolution, in addition to the light wavelength limit.…”