Lower Josephson critical field in granular HTS measured by microwave absorption

Abstract

Abstrar The method of magnetically modulated microwave absorption (MMMA) has been used here to measure the lower Josephson critical field in a YBaCuO superconductor. The measurements based on the changes in the width of the hysteresis of the MMMA signal which were observed while increasing the range of the magnetic field sweep were carried out. The effects observed by us are explained using the Clem model of the cubic array of superconducting grains. Also, a simple interpretation of the influence of the magnetic modulation on the measured value of the lower Josephson critical field is provided.

Magnetic field modulated microwave spectroscopy across phase transitions and the search for new superconductors

“…The non-resonant absorption measurements at low magnetic field were mostly devoted to the understanding of the hysteresis mechanism and the role of the granularity of the new high temperature superconductors [41,[46][47][48][49]. The main loss mechanisms are usually explained in terms of weakly coupled superconducting domains, i.e.…”

“…Modulated microwave absorption on temperature sweep mode has been used to measure twin boundaries in high-T c superconductors [49,64], Bi 2 Sr 2 CaCu 2 O whiskers [65], powder and bulk MgB 2 [66,67], organic superconductors [68], and more recently, ternary borides Mo 2 Re 3 B and Mo 3 Re 2 B [69]. Correlation of the MFMMS signal with the dc magnetization [70] and comparison with the direct absorption technique (no modulation) was addressed for YBa 2 Cu 3 O 7−x [71,72].…”

Inter- and intragrain effects in superconducting ceramics studied by Modulated Microwave Absorption

“…In conventional magnetic measurements, the sampie is usually cooled down at zero magnetic field, then the magnetic field is applied, and, after the magnetic field removal, the remanent flux trapped in the sample is measured. Recently, an application of the rnicrowave absorption measurements analogous to conventional magnetic measurements has been proposed [29,30]. The method enabled detailed studies of the inter-and intragrain effects, and determination of Josephson critical fields.…”

“…The reversible (a) and irreversible (b) MMMA signal for different magnetic field sweep range (see also[30]). …”