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Josephson effect in heterostructure WITH ANTIFERROMAGNETIC inTerlayer

K. E. Lahmanski1, G. A. Ovsyannikov1, Y.V. Kislinski1, A.V. Shadrin1, K.Y.
Constantinian1,.

1 Kotel`nikov Institute of Radio Engineering and Electronics Russian
Academy of Sciences,
11-7 Mokhovaya s. 125009 Moscow, Russia.
e-mail: kraver@hitech.cplire.ru

It was experimentally shown that Josephson effect take place in
heterostructures Nb/Au/Ca0.5Sr0.5CuO2/YBa2Cu3O7-( (Nb/Au/CSCO/YBCO) with
antiferromagnetic CSCO layers, which were 10(50 nm in thickness dM.
Characteristic length of decay of critical current (IC) with the dM grows
was in order of 10 nm[1], which was much longer, than the length in
heterostrucutres with ferromagnetic interlayer. Normal state interface
resistivities of the heterostructures (RNA, A is an area of heterosructure
) significantly increases with thickness of CSCO layer.
A second harmonic in relation between superconducting current and phase
difference of order parameters across the heterojunctions (CPR) was
observed [2]. In presence of the harmoinic, the CPR are as following :
IS=IC1sin(()+IC2sin(2(). In the case if the harmonic is large and negative:
q=IC2/IC1( -1/2 two ground states of the junction take place: with phase
difference +( and with the difference -( [3]. Such (-junctions, which have
two stable states, can be used for design of quantum bit elements for
quantum computation [4]. The observed harmonics in the heterojunctions with
q= -0.1(-0.2 were too small for (-junctions formation.
An increase of second harmonic characteristic voltage VC2=IC2RN
proportional to transparency D of the junction was predicted [5]. The
transparency is inversely proportional to the normal state interface
resistivity of junction D(1/(RNA). NdBaCu3O7 bottom layer with small
surface roughness was used instead of YBCO film with aim to obtain
structures with thinner CSCO layers and smaller RNS. Correlation between
characteristic voltages: VC=ICRN, VC2=IC2RN and the normal state
resistivities RNA will be discussed.
The study is supported in part by programs of Physics Department and
the Presidium of Russian Academy of Sciences, Europian Community program
(project No. NMP3-CT-2006-033191), as well as by the President of the
Russian Federation (grant No. NSh-5408.2008.2), RFBR project No. 08-02-
00487, and International Center of Science and Technology grant No. 3743.

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(2007).
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