Calibration of the open-flat coil-based tunnel diode oscillator technique (OFC magnetometer) for quantitative extraction of physical characteristics of superconductive state

Citation
Sg. Gevorgyan et al., Calibration of the open-flat coil-based tunnel diode oscillator technique (OFC magnetometer) for quantitative extraction of physical characteristics of superconductive state, PHYSICA C, 366(1), 2001, pp. 6-12
Citations number
10
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
PHYSICA C
ISSN journal
0921-4534 → ACNP
Volume
366
Issue
1
Year of publication
2001
Pages
6 - 12
Database
ISI
SICI code
0921-4534(200112)366:1<6:COTOCT>2.0.ZU;2-K
Abstract
We are developing a flat coil-based tunnel diode oscillator technique, whic h can be used for detection of changes of distances with similar to1 Angstr om absolute and similar to 10(-6) relative resolution. It is also an excell ent radio frequency Q-meter for detection of changes similar to 10(-9) W of absorption in small-volume specimens. We are using it for high-resolution study of various weakly expressed peculiarities of the superconductive stat e in thin plate-like HTS (in particular, the peculiarities of vortex motion , allowing determination of some material parameters). But, for correct ext raction of physical characteristics by this sensitive technique there is ne ed to calibrate properly both the shifts in resonant frequency (inductance change) and the amplitude (Q-factor change) for the technique. The problem here is much complicated compared with a solenoid coil-based traditional te chnique. In this report we discuss only the method of calibration of coil's resonant frequency change (testing field's configuration change) with copp er plates, allowing correct transfer of the measured shifts of frequency to changes of distance from the coil face. The results show an exponential de crease of the sensitivity with a distance from the coil. The data allow est imating the optimal sizes for the samples for a given coil design. For such samples the frequency shifts are proportional to the sample area. The data shows also the imperfections of the used flat coil's design causing some d ecrease of sensitivity in a current technique. We discuss ways to make such a perspective technique much better. (C) 2001 Elsevier Science B.V. All ri ghts reserved.