L. A. Chebotkevich

Influence of Induced Anisotropy on the Processes of Magnetization Reversal of Cobalt Circular Nanodots

The magnetic structure and the processes of magnetization reversal of individual cobalt nanodots and arrays of cobalt nanodots have been studied using the magneto-optical Kerr effect and magnetic force microscopy. Arrays of nanodots have been prepared by ion etching from a continuous cobalt film. Magnetic anisotropy is induced during deposition of the cobalt films. The nanodots have the diameter d = 600 nm and the period varying from 1.5d to 3.0d. Magnetic force microscopy images have shown that the induced magnetic anisotropy affects the orientation of magnetization of noninteracting nanodots and the direction of displacement of the magnetic vortex center in the nanodots coupled by the dipole-dipole interaction.

Magnetic Properties of Epitaxial Co Nanodisk Arrays Packed on Atomically Smooth and Vicinal Si Substrates

Arrays of circular nanodisks have been formed from epitaxial Co films deposited on atomically smooth and vicinal Si(111) single crystals by using a focused Ga+ ion beam. The surface roughness has been determined by scanning tunneling microscopy. The coercive force and the processes of magnetization reversal in films and arrays of epitaxial Co nanodisks have been studied. It has been shown that the coercive force of the Co nanodisk arrays on the atomically smooth Si(111) surface is larger and that on the vicinal Si(111) surface is smaller than that in the epitaxial films. The studies of the magnetic structure of the nanodisks by magnetic-force microscopy in combination with the micromagnetic simulation have shown that the processes of magnetization reversal in the nanodisks on the atomically smooth substrates occur through the vortex-like states and, on the vicinal substrates, through the C-type state.

Influence of the surface morphology of single-crystal Si(111) substrates on the magnetic properties of epitaxial cobalt films

The epitaxial films Co(111)/Cu(111)-R30°/Si(111) have been grown on the atomically smooth and vicinal Si(111) surfaces. The roughnesses of the substrate and the cobalt film have been determined using scanning tunneling microscopy. The dependence of the coercive force has been investigated as a function of the azimuthal angle. The dependence of the magnetic anisotropy and the coercive force on the surface roughness has been determined. It has been shown that, in the epitaxial cobalt films deposited on the atomically smooth silicon surfaces, crystalline anisotropy of the 〈110〉 type leads to the isotropy of the magnetization reversal processes. The step-induced uniaxial anisotropy has been observed upon deposition on the vicinal surfaces. The films deposited on the atomically smooth surfaces have a complex domain structure.

Effect of diffusion and stresses on the magnetic properties of multilayer Fe/Pd and Fe/Ge films

Multilayer [Fe/Pd]10 and [Fe/Ge]10 films were studied using ferromagnetic resonance, magnetic-force and atomic-force microscopies, magneto-optical Kerr effect, and X-ray diffraction. It was shown that an increase in the interlayer thickness causes changes in magnetic parameters, such as the induced anisotropy, effective magnetization, coercive force, and the parameters of the fine magnetic structure. Reasons of the changes in the magnetic parameters were established.

Magnetization reversal in an ordered array of ferromagnetic nanodots

The magnetization reversal in an array of Fe nanodots etched from the continuous iron film by a focused Ga+ ion beam has been studied. The size of the dots is 600 nm, and the interdot distances are equal to 3.8 µm, 900 nm, and 700 nm. The energy of the dipole-dipole interaction between the nanodots is estimated for arrays with different periods. It is demonstrated that the mechanisms of magnetization reversal are different in arrays of nanodots with strong and negligible dipole-dipole interactions.

Coercivity and induced anisotropy of multilayer films

The effects of annealing on the crystal and magnetic structures and magnetic properties of Co/Cu/Co films with antiferromagnetic and ferromagnetic coupling between Co layers were studied using transmission electron microscopy, Lorentz microscopy, atomic force microscopy, ferromagnetic resonance, and the magnetic induction method. The components of the coercivity and induced anisotropy of multilayer films are estimated theoretically. It is demonstrated that the behavior of the coercivity and induced anisotropy under thermal treatment is governed by changes in structural defects and indirect exchange.

Effect of the shape anisotropy and configurational anisotropy on the magnetic structure of ferromagnetic nanodots

Processes of magnetization reversal of ordered square arrays of “nanodots” of different geometry coupled by dipole-dipole interaction that were formed by a focused beam of Ga+ ions from continuous polycrystalline Co films have been investigated. It has been established that the magnetic structure upon the magnetization reversal is mainly determined by the shape anisotropy of the nanodots. The round and square nanodots undergo magnetization reversal via a magnetic vortex, whereas the rectangular nanodots demonstrate a finite set of single-domain states depending on the orientations of the external magnetic field and easy axis of magnetization. It has been shown that the magnitude of the switching field of arrays of round and square nanodots and the distribution of switching fields in the system of rectangular nanodots upon magnetization reversal along the easy axis is substantially affected by the configurational anisotropy.

Magnetization reversal of nanodots with different magnetic anisotropy and magnetostatic energy

The arrays of circle and square nanodots were prepared by Ga+ ion-beam etching of thing cobalt films with induced uniaxial magnetic anisotropy. The size of researched nanodots was d=600, 450 and 250 nm that equal or less then radius of ferromagnetic correlation for continuous Co film. The distances l=2d and 3d between center of nanodots in the arrays were taken. The interpretation of experimental magnetic force microscopy data was done by means of micromagnetic simulation and MFM-experiment simulation. Each nanodot of arrays with d=600 nm has multidomain structure at demagnetisation state for l=3d and magnetic vortex for l=2d. For arrays with size of element d<600 nm and l=2d and 3d at same condition occurred only vortex state.

Features of the magnetic properties of Pd/Fe/Pd films and nanodisks

The magnetic properties of Pd/Fe/Pd films and nanodisks with diameter 600 nm fabricated by focused ion beam milling were investigated. A fourth-order anisotropy of magnetization reversal in nanodisk arrays was observed during the experiment. It was demonstrated that the anisotropy occurs due both to the breaking of symmetry of dipole-dipole interactions at array boundaries and to the initiation of inhomogeneous configurations of magnetization in nanodisks.

Effect of the structure and thickness of layers on the magnetic and magnetoresistive properties of Py/Co/Cu/Co nanocrystalline films

AbstractPy/Co1/Cu/Co2 films (Py is the Ni63Co25Fe12 ternary permalloy) were produced by magnetron sputtering on glass substrates. The thicknesses of layers are dCu = 0.7–4 nm, n