Münster 1999 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
TT: Tiefe Temperaturen
TT 21: Postersitzung III: Hochfrequenzeigenschaften (1-4), Amorphe Systeme (5-9), Borkarbide (10-18), Quantenflüssigkeiten (19-25), Dünne Filme (26-49), Vortexdynamik, Pinning (50-63), M-I-Überg
änge, quantenkritische Ph
änomene (64-89)
TT 21.62: Poster
Donnerstag, 25. März 1999, 14:30–18:00, Foy
Global and Local Magnetisation Measurements on Nb Thin Films — •P. Esquinazi1, A. Setzer1, Y. Kopelevich2, D. Fuchs3, E. Zeldov3, and C. Assmann4 — 1Abt. Supraleitung und Magnetismus, Universität Leipzig, 04013 Leipzig — 2Instituto de Fisica, Universidade Estadual de Campinas, 13083-970 Campinas, Brasil — 3Weizmann Institute of Science, 76100 Rehovot, Israel — 4Cryosensoric Laboratory, PTB, 10587 Berlin
In a recently published communication [1] a second magnetisation peak (SMP) in a Nb thin film has been reported. It has been argued that the SMP in Nb and possibly also in some HTSC is due to a thermomagnetic flux jump instability and is not related to an enhancement of the critical current density [1]. To study in detail the development of the SMP and its dependence on geometry we have studied the magnetisation of Nb thin films of thickness between 120 nm and 1.2 µm by means of SQUID and µ-Hall sensor array. We show that the field of the SMP HSMP(T) shifts to higher temperatures the larger the thickness of the film and it vanishes if the film width is small enough in agreement with thermomagnetic instability criteria. Local measurements reveal a dome like flux distribution in the middle of the film after the first flux entry. In some cases the local fields are even larger than the applied field resulting in a smaller magnetisation than the equilibrium one at H < HSMP(T).
Supported by the DFG under INK 24 /B1-1, project H, and by the German-Israeli-Foundation.
[1] Y. Kopelevich and P. Esquinazi, J. Low Temp. Phys. 113, 1 (1998)