### Title, author, abstract

title
Irreversibility Field in Hg-1223 Grain Aligned Powders
authors
Edmund S. Otabe(1), Teruo Matsushita(1,2)
Michael Baenitz(3), Christof Ecker(3), Klaus L\"uders(3)
Eugene V. Antipov(4)
(1)Department of Computer Science and Electronics, Kyushu Institute of Technology,
680--4 Kawazu, Iizuka, 820 JAPAN
(2)Graduate School of Information Science and Electrical Engineering (ISEE), Kyushu University,
6--10--1 Hakozaki, Higashi-ku, Fukuoka 812--81, Japan
(3)Fachbereich Physik, Freie Universit\"at Berlin, Arnimallee 14, D--14195 Berlin, Germany
(4)Department of Chemistry, Moscow State University, 119899 Moscow, Russia
abstract
The crystal axis of Hg-1223 powders was aligned in epoxy resin under a high magnetic field and the irreversibility field, $B_{\rm i}$, was estimated from the onset of the temperature dependence of the fundamental and third harmonic AC susceptibilities under a magnetic field parallel to the $c$-axis. When the temperature dependence of $B_{\rm i}$ is expressed as $[1-(T/T_{\rm c})^2]^n$, $n$ was large at low temperatures and reduced to 1.5 at high temperatures. This behavior is the same as other oxide superconductors and indicates that two kinds of pinning centers work collectively. The flux creep theory with assuming two kinds of pinning centers successfully explains the temperature dependence of $B_{\rm i}$. Comparing the present result with the pinning force density dependence of $B_{\rm i}$ in various oxide superconductors, the dimensionality of Hg-1223 was found to be close to that of Bi-2223 and Hg-1212.
Original paper appears in
10th International Symposium on Superconductivity
October 28--30, 1997
Gifu, Japan