Measurement of higher multipole moments of an inhomogeneous state of a superconductor
TL;DR: The first measurement of contributions from multipole moments higher than the dipole of a non-uniformly magnetized intermediate state of a type I superconductor was reported in this article.
Abstract: We report the first measurement of contributions from multipole moments higher than the dipole of a non-uniformly magnetized intermediate state of a type I superconductor. In the specimen shape studied, these contributions are small compared to that from the dipole and they do not affect in a significant way the magnetization curve obtained using a commercial SQUID magnetometer.
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TL;DR: In this article, a cubic Laves phase superconducting single crystal CeRu 2 was used to measure the magnetic field inhomogeneity in the peak effect regime using Quantum Design SQUID Magnetic Property Measurement System.
Abstract: Detailed magnetisation measurements are presented for a cubic Laves phase superconducting single crystal CeRu 2 . These measurements have been performed in the peak effect regime using Quantum Design SQUID Magnetic Property Measurement System (MPMS). To understand the influence of magnetic field inhomogeneity of this set up, on the measured magnetisation, all the data is recorded for different scan lengths. We clearly demonstrate that some of the anomalous magnetisation results reported in literature are artefacts of field inhomogeneity. We also present a model based on Critical State Model to simulate the effect of field inhomogeneity on the measured magnetisation.
16 citations
TL;DR: In this paper, the authors show that contributions from higher multipole moments are clearly visible in that part of the magnetization hysteresis curve where it crosses the M = 0 axis.
Abstract: The inhomogeneity of the intermediate and the mixed states of type I and type II superconductors can manifest as contributions from multipole moments higher than dipole moment of the specimen to the “measured magnetization signal”. By performing careful magnetization (M) measurements with a SQUID magnetometer on disc-shaped superconducting specimens of lead (type I) and niobium (type II), we show that contributions from higher multipole moments are clearly visible in that part of the magnetization hysteresis curve where it crosses the M = 0 axis.
15 citations
TL;DR: In this paper, a half-scan technique was proposed to measure magnetisation hysteresis loops in the peak-effect regime of superconducting CeRu 2 and 2H-NbSe 2.
Abstract: Magnetisation hysteresis of type II superconductors measured using SQUID-based Magnetic Property Measurement System (MPMS) made by Quantum Design is known to be affected by inhomogeneity in the external field. We present a new method, viz., half-scan technique, for measuring magnetisation hysteresis loops using MPMS. This technique circumvents the problems caused by field inhomogeneity. We have used this technique to measure magnetisation hysteresis loops in the peak-effect regime of superconducting CeRu 2 and 2H-NbSe 2 . The magnetisation hysteresis obtained using half-scan technique is found to be significantly larger than that obtained by conventional MPMS measurements. At very low fields where the extent of field inhomogeneity is not significant and in the reversible region, the results of the half-scan technique are comparable to those obtained using conventional technique. Moreover, hysteresis measurements are shown to be independent of scan length used in the measurement, thus reaffirming that the results are unaffected by the field inhomogeneity.
13 citations
TL;DR: In this article, the first order vortex transition was studied in several YBa2Cu3O7−δ single crystals subjected to different thermal treatments and it was shown that the heights of the magnetization jumps depend not only on the sample preparation but also on the measurement procedure.
Abstract: The magnetization jumps at the first order vortex transition were studied in several YBa2Cu3O7−δ single crystals subjected to different thermal treatments. It turns out that the heights of the magnetization jumps depend not only on the sample preparation but also on the measurement procedure. Using the technique of SQUID magnetometry the dependence of the jump heights on the length of sample movement in the gradiometer was established. The results are interpreted in terms of multipolar magnetic response from the inhomogeneous magnetic state obtained in the field cooling (FC) regime.
3 citations
TL;DR: In this paper, the results of experimental studies on hysteresis in magnetization, thermomagnetic history effects, anomalous variations in magnetic hystresis curves and the decay rates of magnetization obtained under different thermOMH histories in specimens of conventional and high temperature superconductors are presented.
Abstract: The results of experimental studies on hysteresis in magnetization, thermomagnetic history effects, anomalous variations in magnetic hysteresis curves and the decay rates of magnetization obtained under different thermomagnetic histories in specimens of conventional and high temperature superconductors are presented. The Bean’s critical state model is considered adequate to explain magnetic behaviour in conventional hard superconductors. The similarity in the general features of the results of different experiments on specimens of the two families of superconductors underscores the efficacy of the said model to understand some aspects of the macroscopic magnetic response of high temperature superconductors as well. For instance, the isothermal magnetization hysteresis loop which comprises of magnetization curves along forward (−H
max to +H
max) and reverse (+H
max to −H
max) paths define an envelop within which all isothermal magnetization data along different thermomagnetic histories lie. There exist inequality relationship between various field values identified asH
peak,H
I,H
II etc. in isothermal magnetization hysteresis as well as magnetic relaxation data. The entire field span of an isothermal magnetization hysteresis data set can be considered to comprise of three parts corresponding to (M
rem(H)−M
FC(H)+M
ZFC(H)) being equal to, less than or greater than zero, whereM
rem(H) are the remanent magnetization values obtained on reducing field to zero after having the specimen in different applied field (H) values. There are, however some situations amongst thermomagnetic history effects in specimens which show incomplete flux trapping on field cooling, where the critical state model has been found inadequate.
2 citations
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TL;DR: Experimental results and phenomenological theory based on the sponge model for hysteretic high-field superconductors are given in this article, where the response of the supercondors to alternating fields superimposed upon steady fields is studied.
Abstract: Experimental results and phenomenological theory based on the sponge model for hysteretic high-field superconductors are given. After developing the exposition for static magnetization, the response of the superconductors to alternating fields superimposed upon steady fields is studied. (T.F.H.)
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TL;DR: In this article, exact solutions of the critical state model for some sample shapes having nonzero demagnetization factor N are presented for samples in the shape of (i) a sphere (ii) a spheroid (iii) a cylinder of circular cross-section with its axis perpendicular to the field and (iv) a cylindrical cross section of elliptical cross section.
Abstract: We present exact solutions of Bean’s critical state model for some sample shapes having non-zero demagnetization factorN. Virgin and hysteresis magnetization curves are obtained for samples in the shape of (i) a sphere (ii) a spheroid (iii) a cylinder of circular cross-section with its axis perpendicular to the field and (iv) a cylinder of elliptical cross section with its axis perpendicular to the field. Some interesting features seen in these first solutions forN ≠ 0 are discussed.
23 citations
12 citations