•Ultrathin films of SrVO3.•Transport and structural properties of ultrathin films of SrVO3 (SVO) on SrTiO3 (001) substrates.•Metal-Insulator Transition (MIT).•Strain relaxation.•Apparition of weak ...antilocalization in ultrathin films.
Transport and structural properties of ultrathin films of SrVO3 (SVO) on SrTiO3 (001) substrates have been investigated and correlations between Metal-Insulator Transition (MIT) and strain relaxation have been studied. Below a critical thickness, when the film is subjected to tensile strain, the resistivity of the films is increasing with decreasing film thickness. Transport properties evolve from metallic to strongly localized state in several monolayer thick films, showing the bandwidth W control of the Mott-Hubbard transition with the film thickness. Furthermore, a dimensional crossover from 3 Dimensions to 2 Dimensions has been studied by transport measurements. Using Quantum Corrections to the Conductivity (QCC), it is demonstrated that MIT is due to renormalized electron-electron interaction in this material. Finally, for films with the thickness below 6nm, the confinement provides new effect in magnetotransport with apparition of weak antilocalization in ultrathin films.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Bismuth iron garnet (BIG), i.e., Bi3 Fe5 O 12, is a strong ferrimagnet that also possesses outstanding magneto-optical properties such as the largest known Faraday rotation. These properties are ...related with the distribution of magnetic moments on octahedral and tetrahedral sites, the presence of spin gaps in the density of state, and a strong spin-orbit coupling. In this work, first-principles ab initio calculations are performed to study the structural, electronic, and magnetic properties of BIG using density functional theory with " Hubbard + U " ( DFT + U ) correction including spin-orbit coupling and hse06 hybrid functional. We found that the presence of spin gaps in the electronic structure results from the interplay between exchange and correlation effects and the crystal field strengths for tetrahedral and octahedral iron sublattices. The DFT + U treatment tends to close the spin gaps for larger U due to overlocalization effects, notably in the octahedral site. On the other hand, the hybrid functional confirms the occurrences of three spin gaps in the iron states of the conduction band as expected from optical measurements. A strong exchange splitting at the top of the valence bands associated with a lone-pair type mixture of O p and Bi s , p states is also obtained. Similar exchange splitting was not previously observed for other iron based garnets, such as for yttrium iron garnet. It follows that hole doping, as obtained by Ca substitution at Bi sites, results in a full spin polarized density at the Fermi energy. This work helps to shed more light on the theoretical comprehension of the properties of BIG and opens the route towards the use of advanced many body calculations to predict the magneto-optical coupling effects in BIG in a direct comparison with the experimental measurements.
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Controlling the magnetization dynamics at the fastest speed is a major issue of fundamental condensed matter physics and its applications for data storage and processing technologies. It requires a ...deep understanding of the interactions between the degrees of freedom in solids, such as spin, electron, and lattice as well as their responses to external stimuli. In this paper, we systematically investigate the fluence dependence of ultrafast magnetization dynamics induced by below-bandgap ultrashort laser pulses in the ferrimagnetic insulators BixY3-xFe5O12 with 1 xBi 3. We demonstrate subpicosecond demagnetization dynamics in this material followed by a very slow remagnetization process. We prove that this demagnetization results from an ultrafast heating of iron garnets by two-photon absorption (TPA), suggesting a phonon-magnon thermalization time of 0.6 ps. We explain the slow remagnetization timescale by the low phonon heat conductivity in garnets. Additionally, we show that the amplitudes of the demagnetization, optical change, and lattice strain can be manipulated by changing the ellipticity of the pump pulses. We explain this phenomenon considering the TPA circular dichroism. These findings open exciting prospects for ultrafast manipulation of spin, charge, and lattice dynamics in magnetic insulators by ultrafast nonlinear optics.
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Based on micromagnetic simulations and experimental observations of the magnetization and lattice dynamics after the direct optical excitation of the magnetic insulator Bi : YIG or indirect ...excitation via an optically opaque Pt/Cu double layer, we disentangle the dynamical effects of magnetic anisotropy and magneto-elastic coupling. The strain and temperature of the lattice are quantified via modeling ultrafast x-ray diffraction data. Measurements of the time-resolved magneto-optical Kerr effect agree well with the magnetization dynamics simulated according to the excitation via two mechanisms: the magneto-elastic coupling to the experimentally verified strain dynamics and the ultrafast temperature-induced transient change in the magnetic anisotropy. The numerical modeling proves that, for direct excitation, both mechanisms drive the fundamental mode with opposite phase. The relative ratio of standing spin wave amplitudes of higher-order modes indicates that both mechanisms are substantially active.
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We have studied the influence of the argon cluster ion sputtering technique in the X-ray photoelectron spectroscopy (XPS) depth-profiling analysis of a strontium titanate SrTiO3 (STO) substrate, ...chosen as a prototype perovskite-type oxide material. Unlike “standard” sputtering technique using monatomic ions, a gentle digging through STO (without inducing a large amount of defects) has been evidenced. Several improvements are evidenced by using this low-energy abrasion process: (i) the absence of argon implantation, (ii) the creation of very few oxygen vacancies which lead in the classical way to the lowering of oxidation states of titanium and the appearance of in-gap electronic states, and (iii) the preservation of the cationic stoichiometry. In addition, electrical measurements confirm that no metal–insulator transition is evidenced using the cluster ion source, unlike the case of the monatomic ion etching. Furthermore, for the latter case, a relaxation effect of the Ar+ ion induced electronic properties has been evidenced by combining XPS and transport measurements. Due to its unique depth-profiling features, the cluster ion sputtering technique offers new insights in the chemical and physical analysis of sensitive oxide surfaces and buried interfaces as in oxide heterostructures and superlattices.
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In patients with left ventricular dysfunction, atrial fibrillation and flutter (AF and AFl, respectively) are common arrhythmias associated with increased morbidity and mortality. The present study ...investigated the potential of dofetilide in AF-AFl patients with left ventricular dysfunction to restore and maintain sinus rhythm, which might reduce mortality and hospitalizations.
In the Danish Investigations of Arrhythmia and Mortality ON Dofetilide (DIAMOND) studies, 506 patients were in AF-AFl at baseline. Over the course of study, cardioversion occurred in 148 (59%) dofetilide- and 86 (34%) placebo-treated patients. In these patients, the probability of maintaining sinus rhythm for 1 year was 79% with dofetilide versus 42% with placebo (P<0.001). Dofetilide had no effect on all-cause mortality, but restoration and maintenance of sinus rhythm was associated with significant reduction in mortality (risk ratio RR, 0.44; 95% CI, 0.30 to 0.64; P<0.0001). In addition, dofetilide therapy was associated with a significantly lower risk ratio versus placebo for either all-cause (RR, 0.70; 95% CI, 0.56 to 0.89; P</=0.005) or congestive heart failure (RR, 0.69; 95% CI, 0.51 to 0.93; P</=0.02) rehospitalization.
Dofetilide is safe and increases the probability of obtaining and maintaining sinus rhythm in patients with structural heart disease. The present study suggests that restoration of sinus rhythm is associated with improved survival.
Abstract Objectives Cardiac cachexia (CC) is associated with changes in body composition. Lipolysis and increased energy expenditure caused by A- and B natriuretic peptides (NPs) have been suggested ...to play a role in CC. We tested the hypothesis that neurohormones and adipokines are associated with body composition in CC and that a progressive loss of fat free mass (FFM) and fat mass (FM) takes place. Methods Body composition with regard to FFM, FM, and body fat distribution was assessed by dual energy X-ray absorptiometry (DXA) in 19 non-diabetic patients with chronic heart failure (CHF) and CC and 38 controls (non-cachectic CHF and individuals with prior myocardial infarction-both n = 19) who were followed for 12 months. Biomarkers of neurohormonal stimulation, inflammation, and endothelial dysfunction were measured. Results N-terminal proBNP (NT-proBNP), midregional proANP (MR-proANP), and total adiponectin were elevated in CHF (p < 0.001) and correlated inversely to BMI and FM. An inverse correlation was observed between pro-adrenomedullin (MR-proADM) and FFM. During follow up body weight was unaltered in all groups even though FM increased by 1.35 kg (p < 0.05) and FFM decreased by 0.5 kg (p < 0.05) in CC patients. The latter correlated inversely to baseline NT-proBNP, MR-proANP, and MR-proADM (p < 0.05). No correlation to changes in FM was found. Conclusions FM was associated with plasma NPs and total adiponectin at baseline; whereas changes in FM and FFM did not correlate to changes in NPs or adiponectin during follow up. Prospectively, FFM decreased but FM increased, despite stable body weight in CC.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Using ultrafast x-ray diffraction, we directly monitor the lattice dynamics induced by femtosecond laser pulses in nanoscale thin films of bismuth iron garnet in external magnetic fields Hext. We ...control the ultrafast laser-induced lattice strain amplitude by changing the laser pulse helicity. The strength of Hext is used as an external parameter to switch the helicity dependence on and off, respectively. Based on magneto-optical spectroscopic measurements, we explain these phenomena by magnetic circular dichroism. Our findings highlight an important approach for ultrafast manipulation of lattice strain in magnetic materials, in particular insulators, and open exciting perspectives towards ultrafast control of lattice strain and heat-induced magnetization switching and spin waves in bismuth substituted iron garnets using the polarization of light.
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A multiscale approach is reported to understand the influence of the Ca and Y co-substitution in Bi-rich iron garnet thin films. Recently, it has been demonstrated that site-selective co-substitution ...of Ca 2+ and Y 3+ in bismuth iron garnet (BIG) leads to either nor p-type semiconductor behavior. However, the evolution of the structural and magnetic properties of bismuth iron garnet upon doping is still unknown. In the (Ca,Y):BIG, thin films grown by pulsed laser deposition onto Gd 3 Ga 5 O 12 substrates, structural investigations confirm the epitaxial growth of doped thin films with high crystallinity and a complete strain relaxation from 20 nm above the film/substrate interface. While x-ray diffraction only evidences a single-phase garnet, the presence of secondary phase nanocrystallites, that are absent in pure BIG grown in similar conditions, is observed by aberration-corrected scanning transmission electron microscopy. These nanocrystallites form in between garnet grains as textured and poorly crystallized hematite. Despite the presence of nanoneedles, Ca and Y co-substitution preserves the giant Faraday rotation of pure BIG and maintains the Curie temperature above 590 K. Only minor energy shifts (80 meV) or small intensity changes (10%) of the Faraday rotation are observed upon doping or annealing and are mainly related to band-gap evolution and cell volume change. Furthermore, the easy magnetization axis rotates towards in the out-of-plane direction upon doping which is also promising for potential applications in spintronics.
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