251 research outputs found
Magnetism in purple bronze LiMoO
Muon spin relaxation measurements around the 25 K metal-insulator transition
in LiMoO elucidate a profound role of disorder as a possible
mechanism for this transition. The relaxation rate and the muon Knight
shift are incompatible with the transition to a SDW state and thus exclude it.Comment: pages 2, fig 2, The conf. on strongly correlated electron systems,
SCES 2004, German
Local Magnetic Susceptibility of the Positive Muon in the Quasi 1D S=1/2 Antiferromagnet KCuF
We report muon spin rotation measurements of the local magnetic
susceptibility around a positive muon in the paramagnetic state of the quasi
one-dimensional spin 1/2 antiferromagnet KCuF. Signals from two distinct
sites are resolved which have a temperature dependent frequency shift which is
different than the magnetic susceptibility. This difference is attributed to a
muon induced perturbation of the spin 1/2 chain.Comment: 13 pages, 4 figures, The 2002 International Conference on Muon Spin
Rotation, Relaxation and Resonance, Virginia. US
Emergent properties hidden in plane view: Strong electronic correlations at oxide interfaces
Finding new collective electronic states in materials is one of the
fundamental goals of condensed matter physics. Atomic-scale superlattices
formed from transition metal oxides are a particularly appealing hunting ground
for new physics. In bulk form, transition metal oxides exhibit a remarkable
range of magnetic, superconducting, and multiferroic phases that are of great
scientific interest and are potentially capable of providing innovative energy,
security, electronics and medical technology platforms. In superlattices new
states may emerge at the interfaces where dissimilar materials meet.
Here we illustrate the essential features that make transition metal
oxide-based heterostructures an appealing discovery platform for emergent
properties with a few selected examples, showing how charge redistributes,
magnetism and orbital polarization arises and ferroelectric order emerges from
heterostructures comprised of oxide components with nominally contradictory
behavior with the aim providing insight into the creation and control of novel
behavior at oxide interfaces by suitable mechanical, electrical or optical
boundary conditions and excitations.Comment: 16 pages, 5 figure
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
Effect of polar discontinuity on the growth of LaNiO3/LaAlO3 superlattices
We have conducted a detailed microscopic investigation of [LaNiO3(1
u.c.)/LaAlO3(1 u.c.)]N superlattices grown on (001) SrTiO3 and LaAlO3 to
explore the influence of polar mismatch on the resulting electronic and
structural properties. Our data demonstrate that the initial growth on the
non-polar SrTiO3 surface leads to a rough morphology and unusual 2+ valence of
Ni in the first LaNiO3 layer, which is not observed after growth on the polar
surface of LaAlO3. A newly devised model suggests that the polar mismatch can
be resolved if the perovskite layers grow with an excess of LaO, which also
accounts for the observed electronic, chemical, and structural effects.Comment: 3 pages, 3 figure
Strain-mediated metal-insulator transition in epitaxial ultra-thin films of NdNiO3
We have synthesized epitaxial NdNiO ultra-thin films in a
layer-by-layer growth mode under tensile and compressive strain on SrTiO
(001) and LaAlO (001), respectively. A combination of X-ray diffraction,
temperature dependent resistivity, and soft X-ray absorption spectroscopy has
been applied to elucidate electronic and structural properties of the samples.
In contrast to the bulk NdNiO, the metal-insulator transition under
compressive strain is found to be completely quenched, while the transition
remains under the tensile strain albeit modified from the bulk behavior.Comment: 4 pages, 4 figure
Orbital control in strained ultra-thin LaNiO/LaAlO superlattices
In pursuit of rational control of orbital polarization, we present a combined
experimental and theoretical study of single unit cell superlattices of the
correlated metal LaNiO and the band insulator LaAlO. Polarized x-ray
absorption spectra show a distinct asymmetry in the orbital response under
strain. A splitting of orbital energies consistent with octahedral distortions
is found for the case of compressive strain. In sharp contrast, for tensile
strain, no splitting is found although a strong orbital polarization is
present. Density functional theory calculations including a Hubbard U term
reveal that this asymmetry is a result of the interplay of strain and
confinement induces octahedral rotations and distortions and altered covalency
in the bonding across the interfacial Ni-O-Al apical oxygen, leading to a
charge disporportionation at the Ni sites for tensile strain.Comment: 4 pages. 5 figure
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