569 research outputs found
Substrate surface engineering for tailoring properties of functional ceramic thin films
Using oxide substrates for functional ceramic thin film deposition beyond
their usual application as chemical inert, lattice-matched support for the
films represents a novel concept in ceramic thin film research. The substrates
are applied as a functional element in order to controllably modify the atom
arrangement and the growth mode of ceramic prototype materials such as cuprate
superconductors and colossal magnetoresistance manganites. One example is the
use of epitaxial strain to adjust the relative positions of cations and anions
in the film and thus modify their physical properties. The other makes use of
vicinal cut SrTiO3 which enables the fabrication of regular nanoscale step and
terrace structures. In YBa2Cu3O7-x thin films grown on vicinal cut SrTiO3
single crystals a regular array of antiphase boundaries is generated causing an
anisotropic enhancement of flux-line pinning. In the case of La-Ca-Mn-O thin
films grown on vicinal cut substrates it could be demonstrated that magnetic
in-plane anisotropy is achieved.Comment: 6 page
On Magnetic Interlayer Coupling and Proximity Effect in a LaCaMnO(10 nm)/YBaCuO(10 nm) Superlattice
We present a study of interlayer coupling and proximity effects in a
LaCaMnO(10 nm)/YBaCuO(10 nm) superlattice.
Using element-sensitive x-ray probes, the magnetic state of Mn can be probed
without seeing the strong diamagnetism of the superconductor, which makes this
approach ideal to study changes in the magnetic properties across the
superconducting transition. By a combined experiment using {\it in situ}
transport measurements during polarized soft x-ray measurements, we were able
to see no noticeable influence of the superconducting state on the magnetic
properties and no evidence for magnetic coupling across a 10 nm YBCO layer.Comment: 4 pages, submitted to Applied Physics Letter
Suppression of Superconductivity in YBCO/LCMO Superlattices
The competition of superconductivity and magnetism in superlattices composed
of alternating YBaCuO and LaCaMnO thin
films is investigated using low-energy optical spectroscopy. The thickness of
the superconducting YBCO layers is varied from 30 nm to 20 nm while the
thickness of the magnetic LCMO layers is kept constant at 20 nm. We clearly
observe that the superconducting condensate density in the superconducting
state of superlattice is drastically reduced by the magnetic subsystem which
may be connected with proximity effects that distort the gap symmetry and thus
suppress superconductivity.Comment: 4 pages, 4 figure
A study of the ferromagnetic transition of in nanometer thick bilayers with , , Au and Cr: Signature of injected carriers in the pseudogap regime
The hypothesis regarding the existence of uncorrelated pre-formed pairs in
the pseudogap regime of superconducting is tested experimentally
using bilayers of and the itinerant ferromagnet . In
our study, we monitor the influence of on , the
ferromagnetic ordering temperature of . Here, is the temperature
of maximum dM/dT or dR/dT where M and R are the magnetization and resistance of
, respectively. We compare the results with similar measurements
carried out on bilayers of , and with
. We find that in bilayers made of underdoped 10 nm /5
nm , the values are shifted to lower temperatures by up to 6-8 K
as compared to K of the 5 nm thick reference film.
In contrast, in the other type of bilayers, which are not in the pseudogap
regime near , only a smaller shift of up to 2 K is observed. These
differences are discussed in terms of a proximity effect, where carriers from
the layer are injected into the layer and vice versa.
We suggest that correlated electrons in the pseudogap regime of
are responsible for the observed large shifts.Comment: 9 figure
Enhancement of flux-line pinning in all-oxide superconductor/ferromagnet heterostructures
We have studied the local critical current density, jc, in the superconductor
thin film of bilayer structures consisting of YBa2Cu3O7 and the ferromagnets
La2/3Ca1/3MnO3 and SrRuO3, respectively, by means of quantitative
magneto-optics. A pronounced hysteresis of jc was observed which is ascribed to
the magnetization state of the ferromagnetic layer. The results are discussed
within the frame of magnetic vortex - wall interactions.Comment: 9 page
Superconductivity in epitaxial thin films of NaxCoO2 y D2O
The observation of superconductivity in the layered transition metal oxide
NaxCoO2 y H2O (K. Takada et al., Nature 422, 53 (2003)) has caused a tremendous
upsurge of scientific interest due to its similarities and its differences to
the copper based high-temperature superconductors. Two years after the
discovery, we report the fabrication of single-phase superconducting epitaxial
thin films of Na0.3CoO2 x 1.3 D2O grown by pulsed laser deposition technique.
This opens additional roads for experimental research exploring the
superconducting state and the phase diagram of this unconventional material.Comment: 3 pages, 5 figure
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