Europhys. Lett.
Volume 75, Number 2, July 2006
Page(s) 294 - 300
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 23 June 2006
Europhys. Lett., 75 (2), pp. 294-300 (2006)
DOI: 10.1209/epl/i2006-10115-8

Subgap magnetotransport in $\chem{Pb/LaCaMnO}$ point contacts

V. N. Krivoruchko, V. Yu. Tarenkov, A. I. D'yachenko and V. N. Varyukhin

Donetsk Physics & Technology Institute NAS of Ukraine Str. R. Luxemburg 72, 83114 Donetsk, Ukraine

received 5 April 2006; accepted in final form 31 May 2006
published online 23 June 2006

Andreev reflection spectroscopy has been used to probe mutual influence of superconductivity and ferromagnetism in contacts of a low-temperature superconductor (S), Pb, and a half-metallic ferromagnet, La0.65Ca0.35MnO3 (LCMO). In the contacts, which we distinguish as proximity-affected ones, a few unusual effects have been detected: i) a spectacular drop in the resistance of the contacts at the onset of the Pb superconductivity; ii) excess current and doubling of the normal-state conductance; iii) subharmonic gap structure; and iv) the ratio of the single-particle gap to the Pb superconducting transition temperature is anomalously large. Microscopically, our results can most reasonably be explained assuming a conversion from spin singlet pairs to spin triplets at the S/LCMO interface and a long-range proximity effect.

74.45.+c - Proximity effects; Andreev effect; SN and SNS junctions.
74.78.Fk - Multilayers, superlattices, heterostructures.
74.50.+r - Tunneling phenomena; point contacts, weak links, Josephson effects.

© EDP Sciences 2006