Strain-induced insulator state in La_0.7Sr_0.3CoO_3

We report on the observation of a strain-induced insulator state in ferromagnetic La_0.7Sr_0.3CoO_3 films. Tensile strain above 1% is found to enhance the resistivity by several orders of magnitude. Reversible strain of 0.15% applied using a piezoelectric substrate triggers huge resistance modulations, including a change by a factor of 10 in the paramagnetic regime at 300 K. However, below the ferromagnetic ordering temperature, the magnetization data indicate weak dependence on strain for the spin state of the Co ions. We interpret the changes observed in the transport properties in terms of a strain-induced splitting of the Co e_g levels and reduced double exchange, combined with a percolation-type conduction in an electronic cluster state

Reversible strain effect on the magnetization of LaCoO3 films

The magnetization of ferromagnetic LaCoO3 films grown epitaxially on piezoelectric substrates has been found to systematically decrease with the reduction of tensile strain. The magnetization change induced by the reversible strain variation reveals an increase of the Co magnetic moment with tensile strain. The biaxial strain dependence of the Curie temperature is estimated to be below 4K/% in the as-grown tensile strain state of our films. This is in agreement with results from statically strained films on various substrates

Strain-controlled switching kinetics of epitaxial PbZr0.52Ti0.48O3 films

We investigate the effect of biaxial strain on the switching of ferroelectric thin films. The strain state of epitaxial PbZr0.52Ti0.48O3 films is controlled directly and reversibly by the use of piezoelectric Pb(Mg1/3Nb2/3)0.72Ti0.28O3 (001) substrates. At small external electric fields, the films show switching characteristics consistent with a creep-like domain wall motion. In this regime, we find a huge decrease of the switching time under compressive strain. For larger external electric fields, the domain wall motion is in a depinning regime. The effect of compressive strain is more moderate in this region and shows a reduction in the switching kinetics

Wide-range strain tunability provided by epitaxial LaAl1−xScxO3 template films

The dielectric diamagnetic LaAl1− xScxO3 (LASO) (x=0–1) is proposed for adjusting of the biaxial in-plane lattice parameter of oxide substrates in the wide range from 3.79 to 4.05 Å (6.5%). This range includes the pseudocubic lattice parameters of most of the currently investigated complex oxides. The in-plane lattice parameter of strain-relaxed LASO films depends linearly on the composition, and these films grow with a smooth surface. On several different LASO-buffered substrates, ferromagnetic La0.7Sr0.3MnO3 (LSMO) films have been grown in predetermined strain states. A series of 30 nm thick LSMO films on LASO-buffered LaSrAlO4(001) demonstrates that continuously controlled coherent strains in a wide range, in this case from − 1 to +0.6%, can be obtained for the functional oxide films grown on LASO

Thickness-dependent Ru exchange spring at La_0.7Sr_0.3MnO₃–SrRuO₃ interface

The conducting oxide ferromagnets SrRuO3 (SRO) and LaSr0.3MnO3 (LSMO) form a Ru exchange spring at a coherent low‐interdiffusion interface grown on TiO2‐terminated SrTiO3(STO)(001) substrates as SRO(d)/LSMO/STO(001) bilayers. Field‐ and temperature‐dependent magnetization data with systematically varied thickness d of SRO from 7 to 18 unit cells (uc) indicate a thickness of 10–14 uc of the exchange spring which governs magnetic switching and causes thickness‐dependent field‐cooling effects. Mn L3 edge X‐ray magnetic circular dichroism (XMCD) data reveal the dominating in‐plane orientation of interfacial spins. In low magnetic fields, noncoplanar, topologically nontrivial spin textures arise and can be switched, driven by the Zeeman energy of the LSMO layer

Binding energy referencing for XPS in Alkali metal-based battery materials research (II): Application to complex composite electrodes

X-ray photoelectron spectroscopy (XPS) is a key method for studying (electro-)chemical changes in metal-ion battery electrode materials. In a recent publication, we pointed out a conflict in binding energy (BE) scale referencing at alkali metal samples, which is manifested in systematic deviations of the BEs up to several eV due to a specific interaction between the highly reactive alkali metal in contact with non-conducting surrounding species. The consequences of this phenomenon for XPS data interpretation are discussed in the present manuscript. Investigations of phenomena at surface-electrolyte interphase regions for a wide range of materials for both lithium and sodium-based applications are explained, ranging from oxide-based cathode materials via alloys and carbon-based anodes including appropriate reference chemicals. Depending on material class and alkaline content, specific solutions are proposed for choosing the correct reference BE to accurately define the BE scale. In conclusion, the different approaches for the use of reference elements, such as aliphatic carbon, implanted noble gas or surface metals, partially lack practicability and can lead to misinterpretation for application in battery materials. Thus, this manuscript provides exemplary alternative solutions

Untangling the hedge: Genetic diversity in clonally and sexually transmitted genomes of European wild roses, Rosa L.

While European wild roses are abundant and widely distributed, their morphological taxonomy is complicated and ambiguous. In particular, the polyploid Rosa section Caninae (dogroses) is characterised by its unusual meiosis, causing simultaneous clonal and sexual transmission of sub-genomes. This hemisexual reproduction, which often co-occurs with vegetative reproduction, defies the standard definition of species boundaries. We analysed seven highly polymorphic microsatellite loci, scored for over 2 600 Rosa samples of differing ploidy, collected across Europe within three independent research projects. Based on their morphology, these samples had been identified as belonging to 21 dogrose and five other native rose species. We quantified the degree of clonality within species and at individual sampling sites. We then compared the genetic structure within our data to current rose morpho-systematics and searched for hemisexually co-inherited sets of alleles at individual loci. We found considerably fewer copies of identical multi-locus genotypes in dogroses than in roses with regular meiosis, with some variation recorded among species. While clonality showed no detectable geographic pattern, some genotypes appeared to be more widespread. Microsatellite data confirmed the current classification of subsections, but they did not support most of the generally accepted dogrose microspecies. Under canina meiosis, we found co-inherited sets of alleles as expected, but could not distinguish between sexually and clonally inherited sub-genomes, with only some of the detected allele combinations being lineage-specific

The Copernicus surface velocity platform drifter with barometer and reference sensor for temperature (SVP-BRST): genesis, design, and initial results

To support calibration and validation of satel- lite sea surface temperature (SST) retrievals, over 60 high- resolution SST (HRSST) drifting buoys were deployed at sea between 2012 and 2017. Their data record is reviewed here. It is confirmed that sea state and immersion depth play an important role in understanding the data collected by such buoys and that the SST sensors need adequate insu- lation. In addition, calibration verification of three recovered drifters suggests that the sensor drift is low, albeit negative at around −0.01 K year−1. However, the statistical significance of these results is limited, and the calibration procedure could not be exactly reproduced, introducing additional uncertain- ties into this drift assessment. Based on lessons learnt from these initial buoys, a new sensor package for the Surface Velocity Platform with Barometer (SVP-B) was designed to serve calibration of SST retrievals by European Union’s Copernicus satellites. The novel sensor package includes an HRSST sensor calibrated by a metrology laboratory. The sensor includes a pressure probe to monitor immersion depth in calm water and acquires SST data at 1 Hz over a 5 min in- terval every hour. This enables the derivation of mean SST as well as several percentiles of the SST distribution. The HRSST sensor is calibrated with an uncertainty better than 0.01 K. Analysis of the data collected by two prototypes de- ployed in the Mediterranean Sea shows that the buoys are able to capture small-scale SST variations. These variations are found to be smaller when the sea state is well mixed and when the buoys are located within eddy cores. This affects the drifter SST data representativeness, which is an aspect of importance for optimal use of these data

An Ambystoma mexicanum EST sequencing project: analysis of 17,352 expressed sequence tags from embryonic and regenerating blastema cDNA libraries

BACKGROUND: The ambystomatid salamander, Ambystoma mexicanum (axolotl), is an important model organism in evolutionary and regeneration research but relatively little sequence information has so far been available. This is a major limitation for molecular studies on caudate development, regeneration and evolution. To address this lack of sequence information we have generated an expressed sequence tag (EST) database for A. mexicanum. RESULTS: Two cDNA libraries, one made from stage 18-22 embryos and the other from day-6 regenerating tail blastemas, generated 17,352 sequences. From the sequenced ESTs, 6,377 contigs were assembled that probably represent 25% of the expressed genes in this organism. Sequence comparison revealed significant homology to entries in the NCBI non-redundant database. Further examination of this gene set revealed the presence of genes involved in important cell and developmental processes, including cell proliferation, cell differentiation and cell-cell communication. On the basis of these data, we have performed phylogenetic analysis of key cell-cycle regulators. Interestingly, while cell-cycle proteins such as the cyclin B family display expected evolutionary relationships, the cyclin-dependent kinase inhibitor 1 gene family shows an unusual evolutionary behavior among the amphibians. CONCLUSIONS: Our analysis reveals the importance of a comprehensive sequence set from a representative of the Caudata and illustrates that the EST sequence database is a rich source of molecular, developmental and regeneration studies. To aid in data mining, the ESTs have been organized into an easily searchable database that is freely available online