A.V. Davydenko

Optimal Cu buffer layer thickness for growing epitaxial Co overlayers on Si(111)7 × 7

Using scanning tunneling microscopy, reflection high energy diffraction and magnetic optical Kerr effect measurements, growth mode and the magnetic properties of epitaxial Co films on Si(111) with epitaxial Cu(111) buffer layers of various thicknesses have been studied. The strained 3.5-monolayer-thick Cu/Si(111) film has been found to be an optimal buffer, in which case an almost ideal layer-by-layer like growth of Co is observed up to six Co monolayers, due to a negligible lattice mismatch. The coercivity of Co films grown in this layer-by-layer like fashion has been determined to be about 10 Oe, testifying to the high quality of the formed Co film and Co/Cu interface. Changeover of the Co film growth mode from layer-by-layer like to multilayer has been found to result in the transition of the film magnetic properties from isotropic to markedly uniaxially anisotropic.

Magnetization Reversal in the Single Epitaxial Co(111) Nanowires With Step-Induced Anisotropy

A systematic investigation of the magnetization reversal processes is carried out for the single epitaxial Co(111) nanowires possessing step-induced magnetic anisotropy with the easy direction of magnetization oriented perpendicular to the long wire axis. Wires of varying width (500-1800 nm) were patterned by focus ion-beam etching. We separated 3 regions of the NW width: the first is characterized by dominating step-induced magnetic anisotropy, in the second shape anisotropy prevails and in the third two anisotropies are in competition. We establish experimentally mechanisms of the magnetization reversal in the Co(111) nanowires in the directions of magnetic field parallel and perpendicular to the long wire axis in each separated region.

Spatial modulation of in-plane magnetic anisotropy in epitaxial Co(111) films grown on macrostep-bunched Si(111)

We compared magnetic properties of epitaxial Co(111) films grown on microstep- and macrostep-bunched vicinal Si(111) substrates. A surface of the microstep-bunched Si(111) substrate represents regular array of step-bunches with height of 1.7 nm divided from each other by flat microterraces with a width of 34 nm. A surface of the macrostep-bunched Si(111) substrate is constituted by macrostep bunches with a height of 75–85 nm divided by atomically flat macroterraces. The average sum width of a macrostep bunch and a macroterrace is 2.3 μm. While in-plane magnetic anisotropy was spatially uniform in Co(111) films grown on the microstep-bunched Si(111), periodic macromodulation of the topography of the Si(111) substrate induced spatial modulation of in-plane magnetic anisotropy in Co(111) film grown on the macrostep-bunched Si(111) surface. The energy of uniaxial magnetic anisotropy in the areas of the Co(111) film deposited on the Si(111) macrosteps was higher more than by the order of magnitude than the ene...

Experimental evidence of skyrmion-like configurations in bilayer nanodisks with perpendicular magnetic anisotropy

Formation and existence of magnetic skyrmion-like configurations in bilayer nanodisks {Ta(3 nm)/[Co(0.37 nm)/Ni(0.58 nm)]10}2 with perpendicular magnetic anisotropy are shown experimentally at room temperature. Magnetization reversal through the skyrmion state is studied using magnetic hysteresis measurements. An evolution of skyrmion configurations in the nanodisk structure is analyzed. Experimental methods and micromagnetic simulations help to understand the magnetization reversal processes occurring through the stable skyrmion-like configurations. Formation of the intermediate C-states during magnetization reversal is demonstrated. The skyrmion number for all possible spin configurations is calculated.

The structure and magnetic properties of Co films on Si(111) and Si(001) substrates

Epitaxial Co films have been grown on single-crystal Si(111) and Si(001) substrates. The structure and the lattice parameter of Co films have been determined using the method of reflection high-energy electron diffraction. The domain structure of the epitaxial Co films has been studied, and the presence of a magnetocrystalline anisotropy and an anisotropy induced by substrate steps have been established. It has been shown that the coercive force of epitaxial Co films is determined by the roughness of the surface and by misfit dislocations.

Microstructure evolution and magnetic behavior of self-organized arrays of ultra-high aspect ratio epitaxial Co nanostrips

The arrays of magnetic nanowires (NWs) and nanostrips (NSs) with uniaxial anisotropy are good candidates to be used in domain wall propagation based devices, magnetic storage media with high recording density, GMR sensors and biomedical assays [1,2].

Atomic-scale surface engineering for enhancement of the Dzyaloshinskii-Moriya Interaction in thin films with 3d-5d(4d) interfaces

An interface between 3d transition metal and 5d(4d) heavy metal (HM) is a host of intriguing spin-related effects desirable for spin-orbitronic applications [1].