Sg. Gevorgyan et al., The possibility of detection of small absorption in HTS thin films by means of the highly sensitive OFC magnetometer, PHYSICA C, 363(2), 2001, pp. 113-118
We have essentially widened the capabilities of the open-flat coil-based tu
nnel diode oscillator technique (OFC magnetometer) for simultaneous tests o
f magnetic penetration depth, A, of rf magnetic field and for detection of
small changes of absorption inside the thin plate-like HTS materials. The u
pdated method is based on simultaneous detection of the inductance and Q-fa
ctor value changes of the unusual flat (single-layer open-faced geometry) c
oil-based MHz-range resonator, which finally leads to the resonant frequenc
y and amplitude changes of the oscillator. Our technique enables detecting
the changes similar to 10(-12) H of HTS film's magnetic inductance (the cha
nges similar to1-3 Angstrom of lambda). It detects also the changes similar
to 10(-9) W of testing field's power absorption by the film, originated fr
om the variation of its internal flux distribution (due to vortex flow duri
ng the suppression of superconductivity by external magnetic field). It can
operate in wide ranges of temperature and magnetic field and measure in wi
de dynamic ranges of the testing parameters. We present the test results of
the 0.2 mum thick and a few millimeter in diameter disk- and ring-shaped Y
BaCuO films illustrating wide capabilities of the updated OFC magnetometer
to study weakly expressed peculiarities of superconductive state related, i
n particular, with the insignificantly small absorption at vortex motion. (
C) 2001 Elsevier Science B.V. All rights reserved.