CARS-background suppression by phase-controlled nonlinear interferometry.

We have developed a new technique for efficient suppression of the nonresonant background in coherent anti-Stokes Raman scattering (CARS). The advantage of this technique, which is based upon phase-controlled superposition of an appropriately selected reference signal, is presented in theory and demonstrated experimentally by the example of the S(3) (pure rotational) transition of molecular hydrogen

Anisotropic second-order nonlinearities of organic monolayers.

Monolayers prepared from hemicyanine chromophores of high second-order nonlinearity (β=1.3×10−26 esu at resonance) have been used to study anisotropies of the concomitant χ(2)-susceptibility tensor. All components of this third-rank tensor have been determined by Fourier analysis of the anisotropic coverage density Ns(φ) with respect to the angle of rotation about surface normal. Depending on the preparation both Cs and C2v symmetry could be identified

Spin-polarized current injection induced magnetic reconstruction at oxide interface

Electrical manipulation of magnetism presents a promising way towards using the spin degree of freedom in very fast, low-power electronic devices. Though there has been tremendous progress in electrical control of magnetic properties using ferromagnetic (FM) nanostructures, an opportunity of manipulating antiferromagnetic (AFM) states should offer another route for creating a broad range of new enabling technologies. Here we selectively probe the interface magnetization of SrTiO3/La0.5Ca0.5MnO3/La0.7Sr0.3MnO3 heterojunctions and discover a new spin-polarized current injection induced interface magnetoelectric (ME) effect. The accumulation of majority spins at the interface causes a sudden, reversible transition of the spin alignment of interfacial Mn ions from AFM to FM exchange-coupled, while the injection of minority electron spins alters the interface magnetization from C-type to A-type AFM state. In contrast, the bulk magnetization remains unchanged. We attribute the current-induced interface ME effect to modulations of the strong double-exchange interaction between conducting electron spins and local magnetic moments. The effect is robust and may serve as a viable route for electronic and spintronic applications

Symmetry superposition studied by surface second-harmonic generation.

The components of a third-rank χ(2) tensor have been split into contributions due to 1-fold, 2-fold, 3-fold, and ∞-fold or isotropic rotation axes for a surface of Cs symmetry. Theoretical analysis of the rotation patterns obtained by the surface second-harmonic (SH) generation indicates that a complete symmetry analysis cannot be performed without knowledge of the relevant distribution functions. Rotation axes of lower symmetry create via ‘‘overtones’’ or ‘‘harmonics’’ contributions apparent in the analysis of the rotation axes of higher symmetry. An experimental example is the observation of structural changes of Au(111) surfaces in an aqueous electrolytic environment. Potential-dependent buildup and removal of a Au(111)-(1×23) surface could be monitored in situ and in real time. Symmetry analysis of the SH rotation patterns reveals both contributions due to a 3-fold axis due to the regular (1×1) structure and simultaneously a 1-fold and a 2-fold axis due to the (1×23) reconstruction

Current-driven interface magnetic transition in complex oxide heterostructure

The interfacial spin state of n-type BaTiO3/La0.5Ca0.5MnO3/La0.7Sr0.3MnO3 heterojunction and its dependence on gate voltage is investigated with magnetic second-harmonic generation at 78 K. The injection of minority spins alters the interface magnetization of La0.7Sr0.3MnO3 from ferromagnetic to antiferromagnetic exchange coupled, while the bulk magnetization remains unchanged. The emergent interfacial antiferromagnetic interactions are attributed to modulations of the strong double-exchange interaction between conducting electron spins and local magnetic moments. The results will help promote the development of new interface-based functionalities and device concepts. (C) 2017 American Vacuum Society

Interface magnetization transition via minority spin injection

The interface magnetization of n-type BaTiO3/La0.7Sr0.3MnO3 heterojunction is selectively probed by magnetic second-harmonic generation at 80 K. The injection of minority spins at the interface causes a sudden, reversible transition of the spin alignment of interfacial Mn ions from ferromagnetic to antiferromagnetic exchange coupled, while the bulk magnetization remains unchanged. We attribute the emergent interfacial antiferromagnetic interactions to weakening of the double-exchange mechanism caused by the strong Hund\u27s rule coupling between injected minority spins and local magnetic moments. The effect is robust and may serve as a viable route for electronic and spintronic applications. Published by AIP Publishing

New Molecular Collisional Interaction Effect in Low-Energy Sputtering

Y. Yao, Z. Hargitai, M. Albert, R. G. Albridge, A. V. Barnes, J. M. Gilligan, B. Pratt Ferguson, G. Lüpke, V. D. Gordon (currently with UT Austin), and N. H. Tolk are with the Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 -- J. C. Tully is with the Department of Physics and Department of Chemistry, Yale University, New Haven, Connecticut 06520 -- G. Betz and W. Husinsky are with the Institut für Allgemeine Physik, Technische Universität Wien, A-1040 Vienna, AustriaAn unexpected pronounced enhancement is observed in sputtering yields per atom for N2+ compared to N+ from a polycrystalline gold target. This effect is seen when the kinetic energy per projectile atom is below 500 eV and increases as projectile energy decreases to near-threshold energies. Enhancements for O2+ over O+ begin at even lower kinetic energies below 100 eV per atom. This new molecular interaction effect may be explained qualitatively by invoking a simple energy transfer model which involves the vibrational frequency of the molecule and the collisional interaction time. [S0031-9007(98)06668-X]Chemistr