New paramagnetic peculiarity of the superconductive transition detected by a highly sensitive OFC magnetometer

• Published in: Superconductor science & technology 2001-12, Vol.14 (12), p.1009-1013
• Main Authors: Gevorgyan, Samvel G, Kiss, Takanobu, Ohyama, Tomokazu, Inoue, Masayoshi, Movsisyan, Artur A, Shirinyan, Hovsep G, Gevorgyan, Vardan S, Matsushita, Teruo, Takeo, Masakatsu
• Format: Article
• Language: English
• Subjects: Exact sciences and technology; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Magnetic components, instruments and techniques; Magnetometers for susceptibility, magnetic moment and magnetization measurements; Physics
• ISSN: 0953-2048; 1361-6668
• DOI: 10.1088/0953-2048/14/12/305

The improved 'LC-resonator' technique (the open-flat coil magnetometer), based on a low-power stable-frequency tunnel diode oscillator with a single-layer open-faced coil, is sensitive to changes of position. About 1 angstrom absolute and better than 10-6 relative resolution can be reached in distance change measurements. It is an excellent MHz-range scientific instrument with which one may study weakly expressed fine peculiarities of the superconductive state in small-volume thin plate-like HTS. It enables changes to be detected of about 1 pH of the HTS film's magnetic inductance (changes of approx equals 1-3 angstroms of the magnetic penetration depth, l) with high (approx equals 10-6) relative resolution. Owing to the pick-up coil's flat design, relatively low operation frequency and high relative resolution, the present method has advantages over others. It is essential for nondestructive studies of thin flat HTS materials (with a small signal) especially near Tc (at the beginning of the formation of Cooper pairs). A new paramagnetic peculiarity of the superconductive transition has been detected in Y-Ba-Cu-O film, which precedes the well known diamagnetic ejection. A possible explanation of the observed effect is given, and the influence of some external physical parameters on the effect is revealed and discussed. 24 refs.