Solid State Phenomena Vol. 215

Abstract: Spectral dependences of the polar Kerr effect in Co/TiO₂ multilayer films in the spectral range 400--1000 nm have been studied. It is shown that the sign, value, and shape of the magneto-optical spectrum depend on the thickness of a dielectric spacer and the number of layers in the structure. It has been established that the magneto-optical rotation in the Co/TiO₂ films considerably exceeds that in homogeneous Co films. The magneto-optical rotation attains the record value 2θ_k = 7.3 deg in the Co (5 nm)/ TiO₂ (17 nm) layered structure with the number of layer pairs n = 8 at a wavelength of 560 nm.

Abstract: Morphology and structure of the interface in Ni/Ge thin films being due to the mutual diffusion of these elements are investigated with the help of atomic force microscope, high resolution electron microscope and micro-diffraction. Strong effect of interface in magnetic behavior of Ni layers is demonstrated and explained by formation of magnetic order in the interface and rough boundaries between layers.

Abstract: In the present work we have investigated the influence of the thermocycling on the magnetoelastic parameters (the ΔЕ-effect) of amorphous Fe₇₅Si₁₀B₁₅ wires, which had been pretreated by dc current j with simultaneous applying of the tensile stresses σ. It was figured out the ΔЕ-effect behavior depends strongly on pretreatment circumstances. Namely, we have got the maximum absolute value of the ΔЕ-effect shifted into direction of the higher magnetic field magnitude at j<39 MA/m² and σ<127 MPa. In addition, the negative ΔЕ-effect was not observed for samples, pretreated at j≥45MА/m² or σ≥128 MPa . The features of such a behavior of the ΔЕ-effect were explained in terms of the magnetoelastic coupling between the inner core and the outer shell of the amorphous wire.

Abstract: In article results of research of the saturation magnetic moment temperature dependence of ferromagnetic amorphous tapes on an iron and cobalt basis, and also one not ferromagnetic amorphous tape are described. It is shown that in an initial condition not all atoms of magnetic elements are in a ferromagnetic phase. Temperature dependence of the saturation moment of a ferromagnetic phase of amorphous tapes is well described by Brillouin's function. Possibility of quantitative definition of part of the magnetic atoms forming not ferromagnetic phase of a tape is proved. It is shown that the tape on the iron basis, containing about 20% of chrome, not ferromagnetic in an initial condition, consists of the superparamagnetic nanoparticles including about 10 atoms of iron.

Abstract: Magnetic properties and ferromagnetic resonance data of (Co₄₁Fe₃₉B₂₀)_x-(SiO₂)_100-x composite films and multilayer structures composed of these films separated by SiC interlayers have been studied. It has been shown that one of the possible causes responsible for the differences of magnetic properties of composites and multilayer structures can be different shapes of magnetic particles and granules in these materials.

Abstract: The effect of physical and technological factors on the effectiveness of the exchange coupling in two-layer film structures such as Fe₂₀Ni₈₀/Fe₅₀Mn₅₀ has been investigated. The dependences of the coercive force and the exchange bias field of permalloy layer on presence of a buffer Ta layer and its thickness, the order of sputtering and the thickness of Fe₂₀Ni₈₀ and Fe₅₀Mn₅₀ layers, substrate temperature and the features of radio-frequency (RF) substrate bias during deposition were investigated. It has been found that the substrate RF bias improves homogeneity of microstructure and reduces the surface roughness of permalloy layer. This in turn increases the magnetic pinning of permalloy layer and creates the prerequisites for the practical application of layered structures with higher thickness of the ferromagnetic layers.

Abstract: In this paper an attempt on the basis of the theory of mobile cellular automata to develop a model of motion of magnetic nanoparticles in human organs and tissues. In the framework of the method of movable cellular automata, the simulated system (tissues and organs) is represented by an assembly of interacting automata (elements of finite size). The concept of the method is based on the introduction of a new state type – the state of a pair of automata. Setting various parameters of the medium (tissues and organs). We can vary behavior of these particles in these mediums.

Abstract: We have evaporated series of Co thin films under vacuum onto silicon and glass substrates at a perpendicular and oblique incidence. The thickness of the magnetic layer ranges from 20 to 400 nm. The static magnetic properties have been performed by means of magnetic force microscopy (M.F.M.) and Alternating Gradient Field Magnetometer (A.G.F.M.) techniques. The influence of the magnetic layer thickness and the deposition angle are studied. As results, it is found a decrease of the coercive field from 250 Oe, for t = 20 nm, to 95 Oe, for t = 400 nm. These H_c values for obliquely evaporated cobalt films are larger than those measured for cobalt films evaporated at normal incidence, found to be equal to a few Oe. It is also found a decrease of the anisotropy field, from 1.6 kOe for the 20 nm Co thick film to 0.95 kOe for the 200 nm Co thick film. Furthermore, an increase of these fields with the increase of the deposition angle is found, as well. The easy axis of the saturation magnetization lies in the film plane, irrespective of the substrate nature. These results, and others, are presented and discussed.

Abstract: We report on experimental results of the temperature dependence of inductive (total) magnetic moment and remanent magnetic moment at saturation field for electrodeposited nanocrystalline Ni films with thicknesses ranging from 350 nm to 20 μm. We have found that the amplitude of roughness and crystallite size significantly affected the remanent saturation magnetic moment and coercivity.

Abstract: We report on magnetization reversal and geometry dependent magnetic anisotropy of Ni nanowire arrays electrodeposited in nanoporous alumina templates. Using micromagnetic simulation we have found that magnetization reversal mechanism in arrays with different nanowire diameters is curling. This magnetic behavior appears with propagation of the domain wall along a nanowire. The calculations have been proven by the analysis of hysteresis curves. To explain magnetic properties of closely-spaced nanowire arrays we have taken into consideration the magnetostatic interaction between adjacent nanowires and their structural defects, like as boundary grains. The investigated magnetic domain pattern of individual bended nanowires confirms rather complicated magnetization reversal mechanism than either coherent rotation of magnetization or its curling. Competition between the shape and magnetoelastic anisotropies can induce an unusual zigzag-like domain pattern in a single nanowire.