Search results for "layer"
showing 10 items of 2667 documents
Molecular Scale Study of Domain Boundaries and Frictional Stick-Slip Motion on Lipid Bilayers
1995
A highly 2-dimensional (2D) anisotropic crystal formation of an organic one component lipid bilayer system is presented measured in air by atomic force microscopy. 2D domains with different crystal orientation could be observed. Their molecularly smooth domain boundaries are perceived to be either commensurable or incommensurable lattice joints. Differences in the orientation of the crystal lattice affects dynamic friction on the micrometer scale. High resolution friction images provide stick-slip motions depending on the scan direction in respect to the lattice orientation. It is shown that sliding friction can be determined by an averaged value of the molecular stick-slip motion of the fr…
Spin-orbit torques and tunable Dzyaloshinskii-Moriya interaction in Co/Cu/Co trilayers
2017
We study the spin-orbit torques (SOTs) in Co/Cu/Co magnetic trilayers based on first-principles density-functional theory calculations in the case where the applied electric field lies in-plane, i.e., parallel to the interfaces. We assume that the bottom Co layer has a fixed in-plane magnetization, while the top Co layer can be switched. We find that the SOT on the top ferromagnet can be controlled by the bottom ferromagnet because of the nonlocal character of the SOT in this system. As a consequence the SOT is anisotropic, i.e., its magnitude varies with the direction of the applied electric field. We show that the Dzyaloshinskii-Moriya interaction (DMI) in the top layer is anisotropic as …
Theoretical investigation of the platinum substrate influence on BaTiO 3 thin film polarisation
2019
Density functional theory calculations are performed to study the out-of-plane polarisation in BaTiO3 (BTO) thin films epitaxially grown on platinum. Prior to any polarisation calculation, the stability of the Pt(001)/BaTiO3(001) structure is thoroughly discussed. In particular, the nature of the Pt/BTO and BTO/vacuum interfaces is characterised. The growth of BTO is shown to start with a TiO2 layer while the nature of the surface termination does not broadly modify the stability. Therefore both upper terminations are considered when describing the ferroelectric behaviour in Pt/BTO interfaces. The geometric and electronic effects of the substrate on the polarisation are investigated. To iso…
An Ising ferromagnet with an antiferromagnetic surface layer: A simple model for magnetic surface reconstruction
1985
Simple cubic Ising lattices are studied by Monte Carlo simulation, using a thin film geometry (usually 40 atomic layers thick), with nearest neighbour ferromagnetic exchange J in the bulk and nearest neighbour antiferromagnetic interaction Js between surface spins. Applying a technique of preferential sampling in the surface layers, we investigate the ordering for a variety of values of JsJ and for various temperatures. For JsAF < Js < − 0.25J (where JsAF ≈ − 2.01J) ferromagnetic ordering occurs at a higher temperature than the antiferromagnetic surface ordering, while for − 0.25J < Js no antiferromagnetic long range order is possible. For Js < JsAF the surface transition occurs at a higher…
Deuterium monolayers physisorbed on krypton-plated graphite: A two-dimensional Ising system
1997
Abstract Neutron-diffraction measurements were used for the first time to investigate the influence of the modification of the graphite substrate potential and of the susbrate symmetry caused by a preadsorbed layer of krypton (Kr). It will be shown that D2 on Kr/graphite presents a new 2D Ising system. The order-disorder transition of this system has been studied.
Threshold photoemission magnetic circular dichroism at the spin-reorientation transition of ultrathin epitaxial Pt/Co/Pt(111)/W(110) films
2009
X-ray magnetic circular dichroism (MCD) is nowadays widely used for the investigation of magnetic properties of surfaces and thin films. Recently, similarly large effects have been observed for UV-VIS MCD effects both in single [1] and two-photon photoemission [2-3]. This threshold MCD effect is directly related to spin-orbit effects present at the Fermi edge. We report on the observation of threshold photoemission magnetic circular dichroism (TPMCD) in one-photon and two-photon photoemission (1PPE and 2PPE) at a Pt-capped ultrathin Co wedge grown on Pt(111)/W(110) using femtosecond laser light. TPMCD measurements result in asymmetries continuously increasing with the sample thickness. This…
Tunable Sign Change of Spin Hall Magnetoresistance in Pt/NiO/YIG Structures
2017
Spin Hall magnetoresistance (SMR) has been investigated in Pt/NiO/YIG structures in a wide range of temperature and NiO thickness. The SMR shows a negative sign below a temperature that increases with the NiO thickness. This is contrary to a conventional SMR theory picture applied to the Pt/YIG bilayer, which always predicts a positive SMR. The negative SMR is found to persist even when NiO blocks the spin transmission between Pt and YIG, indicating it is governed by the spin current response of the NiO layer. We explain the negative SMR by the NiO "spin flop" coupled with YIG, which can be overridden at higher temperature by positive SMR contribution from YIG. This highlights the role of m…
Torsion oscillation magnetometry (TOM) of Fe films on Ni(111)/W(110) substrates
1999
Abstract Fe films 2–20 atomic monolayers (ML) thick have been deposited on Ni(1 1 1) films (4–60 ML) prepared on W(1 1 0) under UHV conditions. The Ni(1 1 1) films grow in a Nishijama–Wassermann orientation with a 3.6% lattice expansion along Ni[2 1 1] (‖ W[1 1 0]). On top of these slightly distorted Ni films iron is observed to grow preferentially in two mirror orientations. The saturation magnetization of these Fe films and the anisotropies of Fe/Ni bilayers have been studied using torsion oscillation magnetometry. The magnetization of the Fe films of 2.13 μB per atom is close to the bulk value of Fe. The out-of-plane surface (interface) anisotropy constant KFeNis=(−0.65±0.15) mJ/m2 of th…
Role of top and bottom interfaces of a Pt/Co/AlOx system in Dzyaloshinskii-Moriya interaction, interface perpendicular magnetic anisotropy, and magne…
2017
We investigate the role of top and bottom interfaces in inversion symmetry-breaking Pt/Co/AlOx systems by inserting ultra-thin Cu layers. Wedge-type ultrathin Cu layers (0-0.5 nm) are introduced between Pt/Co or Co/AlOx interfaces. Interface sensitive physical quantities such as the interfacial Dzyaloshinskii-Moriya interaction (iDMI) energy density, the interfacial perpendicular magnetic anisotropy (iPMA), and the magneto-optical Kerr effects (MOKE) are systematically measured as a function of Cu-insertion layer thickness. We find that the Cu-insertion layer in the bottom interface (Pt/Co) plays a more important role in iDMI, PMA, and MOKE. In contrast, the top interface (Co/AlOx) noticeab…
Observation of quantized subband states and evidence for surface electron accumulation in CdO from angle-resolved photoemission spectroscopy
2008
The electronic structure of well-ordered single-crystal thin films of CdO100 has been studied using angleresolved photoemission spectroscopy. Quantized electron subbands are observed above the valence-band maximum. The existence of these states provides evidence of an intrinsic electron accumulation space-charge layer near the CdO surface, an interpretation supported by coupled Poisson-Schrodinger calculations. The origin of the accumulation layer result is discussed in terms of the bulk band structure of CdO calculated using quasiparticle-corrected density-functional theory, which reveals that the conduction-band minimum at the Brillouin-zone center lies below the charge neutrality level.