The magnetic properties of [Nbx/Niy]5 multilayers (ML) with x = 23 nm and y -2.5, 3.5 and 5.0 nm, were studied using a superconducting quantum interference device (SQUID) magnetometer over the temperature range 2.0 K < T < 300 K, and magnetic field range 0 < H < 3 KOe. All samples exhibited a zero-field superconducting transition temperature Tc near 5.8 K and complex magnetic hysteresis that reflects a strong interplay between Meissner currents, flux trapped in the superconducting Nb layers, and the Ni layer magnetization. The y = 5.0 nm ML exhibited a smooth ferromagnetic hysteresis loop for T > Tc and H applied in the ML plane. In constrast, sharp magnetization jumps of precisely the same magnitude, but opposite polarity, signal abrupt reversals of the ML ferromagnetic moment at two reproducible symmetric switching fields for T just below Tc and H < 1 KOe. The ML with y = 2.5 nm exhibited similar switching fields, but they were obscured by numerous random sharp instabilities in the hysteresis loop just below Tc. Behavior similar to the y = 5. 0 nm sample was observed when the random instabilities disappeared at lower temperatures. These results demonstrate the supercurrent response of superconducting/ferro-magnetic ML is a very sensitive probe of magnetic layer stability and switching dynamics.
|Number of pages||3|
|Journal||IEEE Transactions on Magnetics|
|Issue number||5 II|
|State||Published - Sep 2003|
Bibliographical noteFunding Information:
Manuscript received December 23, 2002. This work was supported in part by the U.S. Department of Energy Office of Science, Division of Materials Sciences under Grant DE-FG02-97ER45653, by the Spanish CICYT under Grant MAT02-04543, and by the ESF Vortex Program.
- Magnetic films
- Magnetic memories
- Magnetic noise
- Metallic superlattices
- Superconducting films
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering