90 research outputs found
Growth of Sr1-xCaxRuO3 thin films by metalorganic aerosol deposition
We report the growth of thin films of Sr1-xCaxRuO3 on SrTiO3 and MgO
substrates by metalorganic aerosol deposition. The structure and microstructure
is characterized by X-ray diffraction and room-temperature scanning tunnelling
microscopy (STM), respectively. STM indicates in-plane epitaxy and a small
surface roughness for films on SrTiO3. The high-quality of the films is
supported by large residual resistivity ratios up to 29.Comment: 4 Pages, 2 Figures, submitted to Proceedings of ICM 2009 (Karlsruhe
Negative refraction in natural ferromagnetic metals
It is generally believed that Veselago's criterion for negative refraction
cannot be fulfilled in natural materials. However, considering imaginary parts
of the permittivity ({\epsilon}) and permeability ({\mu}) and for metals at not
too high frequencies the general condition for negative refraction becomes
extremely simple: Re({\mu}) Re(n) < 0. Here we demonstrate
experimentally that in such natural metals as pure Co and FeCo alloy the
negative values of the refractive index are achieved close to the frequency of
the ferromagnetic resonance. Large values of the negative refraction can be
obtained at room temperature and they can easily be tuned in moderate magnetic
fields
In situ monitoring of atomic layer epitaxy via optical ellipsometry
We report on the use of time-resolved optical ellipsometry to monitor the deposition of single atomic layers with subatomic sensitivity. Ruddlesden–Popper thin films of SrO(SrTiO3) n=4 were grown by means of metalorganic aerosol deposition in the atomic layer epitaxy mode on SrTiO3(1 0 0), LSAT(1 0 0) and DyScO3(1 1 0) substrates. The measured time dependences of ellipsometric angles, Δ(t) and Ψ(t), were described by using a simple optical model, considering the sequence of atomic layers SrO and TiO2 with corresponding bulk refractive indices. As a result, valuable online information on the atomic layer epitaxy process was obtained. Ex situ characterization techniques, i.e. transmission electron microscopy, x-ray diffraction and x-ray reflectometry verify the crystal structure and confirm the predictions of optical ellipsometry
Low-energy electronic properties of clean CaRuO: elusive Landau quasiparticles
We have prepared high-quality epitaxial thin films of CaRuO with residual
resistivity ratios up to 55. Shubnikov-de Haas oscillations in the
magnetoresistance and a temperature dependence in the electrical
resistivity only below 1.5 K, whose coefficient is substantially suppressed in
large magnetic fields, establish CaRuO as a Fermi liquid (FL) with
anomalously low coherence scale. Non-Fermi liquid (NFL) dependence is
found between 2 and 25 K. The high sample quality allows access to the
intrinsic electronic properties via THz spectroscopy. For frequencies below 0.6
THz, the conductivity is Drude-like and can be modeled by FL concepts, while
for higher frequencies non-Drude behavior, inconsistent with FL predictions, is
found. This establishes CaRuO as a prime example of optical NFL behavior in
the THz range.Comment: 12 pages, 21 figures including supplemental materia
Strain-Driven Structure-Ferroelectricity Relationship in hexagonal TbMnO Films
Thin films and heterostructures of hexagonal manganites as promising
multiferroic materials have attracted a considerable interest recently. We
report structural transformations of high quality epitaxial h-TMO/YSZ(111)
films, analyzed by means of various characterization techniques. A phase
transition from P63mc to P63mcm structure at TC~800 K was observed by
temperature dependent Raman spectroscopy and optical ellipsometry. The latter
probing directly electronic system, indicates its modification at the
structural phase transition likely due to charge transfer from oxygen to Mn. In
situ transmission electron microscopy (TEM) of the lamella samples displayed an
irreversible P63mc-P63mcm transformation and vanishing of ferroelectric domains
already at 410 K. After the temperature cycling (300K-1300K-300K) the room
temperature TEM of h-TMO films revealed an inhomogeneous microstructure,
containing ferroelectric and paraelectric nanodomains with P63mc and P63mcm
structure, respectively. We point out a strong influence of stress relaxation,
induced by temperature and by constrained sample geometry onto the structure
and ferroelectricity in strain-stabilized h-TMO thin films.Comment: 24 pages, 10 figure
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