Volume 101, Number 3, February 2013
|Number of page(s)||5|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||15 February 2013|
Supra-oscillatory critical temperature dependence of Nb-Ho bilayers
1 Department of Materials Science and Metallurgy, University of Cambridge - Pembroke Street, Cambridge CB2 3QZ, UK, EU
2 School of Physics and Astronomy, E. C. Stoner Laboratory, University of Leeds - Leeds LS2 9JT, UK, EU
3 School of Physics and Astronomy, University of Minnesota - Minneapolis, MN 55455, USA
4 Michelson Lab, Physics Division, Naval Air Warfare Center - China Lake, CA 93555, USA
Received: 24 October 2012
Accepted: 23 January 2013
We investigate the critical temperature Tc of a thin s-wave superconductor (Nb) proximity coupled to a helical rare-earth ferromagnet (Ho). As a function of the Ho layer thickness, we observe multiple oscillations of Tc superimposed on a slow decay, that we attribute to the influence of the Ho on the Nb proximity effect. Because of the inhomogeneous magnetization in Ho, singlet and triplet pair correlations are present in the bilayers. We take both into consideration when solving the self-consistent Bogoliubov-de Gennes equations, and we find a reasonable agreement with the experiments. We also observe non-trivial transitions into the superconducting state, the zero resistance state being attained after two successive transitions which appear to be associated with the magnetic structure of Ho.
PACS: 74.45.+c – Proximity effects; Andreev reflection; SN and SNS junctions / 74.20.Rp – Pairing symmetries (other than s-wave) / 74.62.-c – Transition temperature variations, phase diagrams
© EPLA, 2013
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