Low Temperature Physics: 32, 824 (2006); https://doi.org/10.1063/1.2219504 (8 pages)
Fizika Nizkikh Temperatur: Volume 32, Number 8-9 (August 2006), p. 1085-1095    ( to contents , go back )

The Andreev spectroscopy of low-temperature superconductor-manganite point contacts

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

A. Galkin Donetsk Physico-Technical Institute of the National Academy of Sciences of Ukraine 72 R. Luksemburg Str., Donetsk 83114, Ukraine
E-mail: krivoruc@krivoruc.fti.ac.donetsk.ua
pos Анотація:

Received February 21, 2006, revised March 9, 2006

Abstract

The Andreev reflection in low-temperature superconductor (Pb or MgB2)—manganite La0.65Ca0.35MnO3 (LCMO) contacts have been investigated. In most cases, typical of superconductor/half-metallic ferromagnet contacts for a voltage range e|V| ≤ DS, where DS is the energy gap of the superconducting injector, an excess voltage Vexc and a suppression of the contact conductivity, G(V) = dI(V)/dV, are observed. However, a number of contacts at e|V| ≤ DS, reveal an increase in conductivity and an excess current in the current-voltage dependences. The behavior of the observed dI(V)/dV dependence in such contacts corresponds to Andreev spectra for a superconductor with an energy gap much larger than that of the injector DS. It is suggested that in such contacts the specific conditions are realized due to which the Cooper pairs penetration from the electrode with a singlet order parameter into the manganite induces a superconducting state with triplet type correlations in the manganite surface region.

PACS:
74.25.+c -
74.78.Fk - Multilayers, superlattices, heterostructures
74.50.+r - Tunneling phenomena; point contacts, weak links, Josephson effects (for SQUIDs, see 85.25.Dq; for Josephson devices, see 85.25.Cp; for Josephson junction arrays, see 74.81.Fa)
75.70.Kw - Domain structure (including magnetic bubbles)

Key words: proximity effect, Andreev reflection, half-metallic ferromagnet, contact spectroscopy, triplet superconductivity.

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