Subgap magnetotransport in point contactsV. 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