Deutsche Tagung f ¨ur Forschung mit ... - SNI-Portal

Nanostrukturen und Grenzflächen Vortrag: Mi., 12:10–12:30 M-V12
Antiphase magnetic proximity effect in perovskite superconductor / ferromagnet
multilayers
Jochen Stahn 1 , Justin Hoppler 2 , Christof Niedermayer 1 , Jacques
Chakhalian 3 , Georg Cristiani 3 , Hans-Ulrich Habermeier 3 , Bernhard
Keimer 3 , Christian Bernhard 2
1 Laboratory for Neutron Scattering, ETH Zürich – 2 Physics department, Université
de Fribourg, Switzerland – 3 Max Planck Institute for Solid State Research, Stuttgart,
Germany
Materials with strongly correlated charge carriers are promising candidates for new
electronic devices because their charge carrier mobility is linked to its spin degree of
freedom and its exchange coupling to magnetic ions. Superconducting materials are
also very attractive since their charge carriers are condensed in a macroscopic quantum
state, the phase of which can be easily manipulated, for example, by an externally
applied magnetic field. Based upon these considerations, heterostructures made from
perovskite-oxides, such as cuprate high Tc superconductors and ferromagnetic manganite
compounds that exhibit the so-called colossal magneto resistance effect seem to
be ideal candidates for novel devices.
Our neutron reflectometry measurements on YBa2Cu3O7/La2/3Ca1/3MnO3 multilayers
have revealed detailed, microscopic information about the magnetization profile as
a function of in-plane and out-of-plane wave vectors. [1] We observed characteristic
differences between the nuclear and the magnetic scattering profiles which in combination
with XMCD [2] results allowed us to identify an antiphase magnetic proximity
coupling where FM moment is induced in YBCO that is oriented antiparallel to the one
in LCMO. We also observed an anomalous enhancement of the off-specular reflection
in the SC state which suggests a strong mutual interaction between the SC and the
FM order parameters.
[1] J. Stahn et.al., Phys. Rev. B 71 (2005) 140509.
[2] J. Chakhalian et.al., Nature Physics 2 (2006) 244.