1,370 research outputs found
Superconductivity in spinel oxide LiTi2O4 epitaxial thin films
LiTi2O4 is a unique material in that it is the only known oxide spinel
superconductor. Although bulk studies have demonstrated that superconductivity
can be generally described by the Bardeen-Cooper-Schreiffer theory, the
microscopic mechanisms of superconductivity are not yet resolved fully. The
sensitivity of the superconducting properties to various defects of the spinel
crystal structure provides insight into such mechanisms. Epitaxial films of
LiTi2O4 on single crystalline substrates of MgAl2O4, MgO, and SrTiO3 provide
model systems to systematically explore the effects of lattice strain and
microstructural disorder. Lattice strain that affects bandwidth gives rise to
limited variations in the superconducting and normal state properties.
Microstructural disorder such as antiphase boundaries that give rise to Ti
network disorder can reduce the critical temperature, but Ti network disorder
combined with Mg interdiffusion can affect the superconducting state much more
dramatically. Thickness dependent transport studies indicate a
superconductor-insulator transition as a function of film thickness regardless
of lattice strain and microstructure. In addition, surface sensitive X-ray
absorption spectroscopy has identified Ti to retain site symmetry and average
valence of the bulk material regardless of film thickness.Comment: 25 pages, 7 figures, v2 - expanded Fig 1,2,7 with added discussion
Strain driven anisotropic magnetoresistance in antiferromagnetic LaSrMnO
We investigate the effects of strain on antiferromagntic (AFM) single crystal
thin films of LaSrMnO (x = 0.6). Nominally unstrained
samples have strong magnetoresistance with anisotropic magnetoresistances (AMR)
of up to 8%. Compressive strain suppresses magnetoresistance but generates AMR
values of up to 63%. Tensile strain presents the only case of a metal-insulator
transition and demonstrates a previously unreported AMR behavior. In all three
cases, we find evidence of magnetic ordering and no indication of a global
ferromagnetic phase transition. These behaviors are attributed to epitaxy
induced changes in orbital occupation driving different magnetic ordering
types. Our findings suggest that different AFM ordering types have a profound
impact on the AMR magnitude and character.Comment: http://dx.doi.org/10.1063/1.489242
Recommended from our members
Phase transitions and magnetic domain coexistence in Nd0.5Sr0.5MnO3 thin films
We present a study of the physical properties of perovskite oxide Nd0.5Sr0.5MnO3 (NSMO) thin films grown on (110)-oriented SrTiO3 substrates. In bulk form, NSMO displays coupled magnetic and electronic transitions from paramagnetic/insulator to ferromagnetic (FM)/metal and then to antiferromagnetic (AFM)/charge-ordered insulator with decreasing temperature. In thin films, the AFM ordering only occurs when the films exist in an anisotropic strain state such as those obtained on (110)-oriented cubic substrates. In this work, resonant X-ray reflectivity, soft X-ray photoemission electron microscopy (X-PEEM), and magnetometry measurements showed that the NSMO film displays both vertical and lateral magnetic phase separation. Specifically, the film consists of three layers with different density and magnetic properties. The FM and AFM properties of the main NSMO layer were probed as a function of temperature using soft X-ray magnetic spectroscopy, and the coexistence of lateral FM and AFM domains was demonstrated at 110 K using X-PEEM
Transient Response of the Induction Coil Loading in the Initial Startup Phase of rf Indiction Thermal Plasmas
Measurement of Space Potential Fluctuation in Edge Plasma of the LHD by Using Emissive Probe made of Carbon Material
Moving-Surface Plasma-Facing Components for Particle Control in Steady-State Magnetic Fusion Devices
Selenidation of epitaxial silicene on ZrB2
The deposition of elemental Se on epitaxial silicene on ZrB2 thin films was investigated with synchrotron-based core-level photoelectron spectroscopy and low-energy electron diffraction. The deposition of Se at room temperature caused the appearance of Si 2p peaks with chemical shifts of n × 0.51 ± 0.04 eV (n = 1-4), suggesting the formation of SiSe2. This shows that capping the silicene monolayer, without affecting its structural and electronic properties, is not possible with Se. The annealing treatments that followed caused the desorption of Se and Si, resulting in the etching of the Si atoms formerly part of the silicene layer, and the formation of bare ZrB2(0001) surface area. In addition, a ZrB2(0001)-(√7 × 3)R40.9° surface reconstruction was observed, attributed to a Se-termination of the surface of the transition metal diboride thin film
Recommended from our members
Modification of magnetocrystalline anisotropy via ion-implantation
The ability to systematically modify the magnetic properties of epitaxial La0.7Sr0.3MnO3 thin films is demonstrated through the use of Ar+ ion implantation. With increasing implant dose, a uniaxial expansion of the c-axis of the unit cell leads to a transition from in-plane toward perpendicular magnetic anisotropy. Above a critical dose of 3 × 1013 Ar+/cm2, significant crystalline disorder exists leading to a decrease in the average Mn valence state and near complete suppression of magnetization. Combined with lithographic techniques, ion implantation enables the fabrication of magnetic spin textures consisting of adjacent regions with tunable magnetic anisotropy in complex oxide thin films
- …