Solid State Phenomena Vols. 233-234

Abstract: Effect of charge carriers concentration on magnetic parameters of the ferromagnetic MnSb nanoclusters as well as opposite effect of cluster magnetization on spin polarization of holes and magnetoresistance were observed in GaSbMn thin films. Microwave magneto-resistance effect is evidence of the charge carriers spin filtering by ferromagnetic clusters.

Abstract: We have investigated the magnetic properties of nanostructured Co-B alloys, that were prepared via electroless deposition. The deposition process results in the formation of a nanostructure consisting of nanotubes connected to thin films at both ends. Depending on the deposition time end-open or end-closed nanotubes can be formed. The overall nanostructure of Co-B deposit has a specific magnetization of 65.6 ± 8 JT^-1Kg^-1 (0.75 ± 0.09 μ_B per Co atom). We also investigated the anisotropy of the nanostructure by carrying out magnetic measurements with and without the top and base films. We only observed magnetic anisotropy in nanostructures with thin films, which had minimum coercivities of 557 A/m (7 Oe) and 4536 A/m (57 Oe) measured parallel and perpendicular to the nanotube axis. The nanotubes do not show any significant anisotropy with coercivities of 8753 A/m (110 Oe) and 7161 A/m (90 Oe) parallel and perpendicular to the nanotube axis.

Abstract: The magnetic and magneto-optical properties of the Co/Si/Co thin-film samples obtained by magnetron sputtering were investigated employing magnetooptical techniques. The thickness of the Co layers was equal to 5 nm, and Si layer thickness varied in the interval of 0.2 to 3.2 nm. The magnetic saturation field of the samples under study was found to oscillate in the magnitude with the change of the Si layer thickness. This result was explained by structural features of the Co/Si/Co multilayers and the presence of the antiferromagnetic exchange coupling between magnetic layers via the silicon interlayer. The peculiarities of the magneto-optical spectra of the Co/Si/Co samples were measured and discussed.

Abstract: Recently we reported interesting phenomenon resulting in formation of irregular polycyclic structures on the surface of Fe or Ni nanoparticles immersed in toluene at ambient conditions. The objectives of the present work were to test the possibility of ambient deposition of carbon on the surface of Fe film, to study the kinetics of the deposition and to characterize the structure of the deposits. Periodic structural and magnetic measurements were performed on the dry samples just taken out of toluene. We observed that carboneous layers on the Fe surface are formed rather fast – they can be initially detected after about one week treatment.

Abstract: A simple model was proposed for description of Cooper pair breaking effect (which is caused by transfer of spin-polarized carriers from the ferromagnetic (FM) manganite into the high temperature superconductor (HTS)) on the critical temperature and the microwave surface impedance of HTS/FM heterostructures. The model is based on the assumption on an exponential dependence of the Cooper pairs concentration (as well as number of the holes in CuO₂ planes, responsible for the superconductivity) on the distance from HTS/FM interface. The model fits well the thickness dependence of HTS film parameters and is used for evaluation of the penetration depth of spin-polarized particles into HTS in the HTS/FM structures.

Abstract: We present the results of macroscopic measurements, X-ray diffraction and neutron reflectivity experiments on ≈ 25 nm thin films of Ni₅₀Mn₃₅In₁₅ grown using Pulsed laser deposition technique on MgO single-crystalline substrate. Intrinsic magnetization of the film below T_c ≈ 290 K was confirmed. Structural measurements show the large temperature-dependent residual strain on the substrate with no indication of martensitic transition.

Abstract: We report on structural and transport properties of Ni-Mn-In thin films. The results obtained have indicated that transport properties of the thin films strongly depend on the structural ordering of the films. Specifically, annealing converts the semiconducting-like character of the resistivity into that typical for metals. This is due to annealing-induced crystallization of as-deposited films which are in partially amorphous state. In both the as-deposited and the annealed thin films the field dependence of the resistivity is negative, which is typical for thin films of Heusler alloys and can be ascribed to the suppression of the spin disorder scattering.

Abstract: We report on the first study of magnetic and structural properties of Co₂Fe_1-xTi_xGa thin films prepared by a magnetron sputtering technique. The presence of well-defined (220) and (422) peaks corresponding to the principal reflection of the Heusler structure were revealed by XRD analysis. Results of magnetic properties measurements of the thin films showed that annealed samples have uniaxial in-plane anisotropy but magnetic properties of as-prepared samples exhibit anisotropy within the plane. The annealed thin films demonstrate complex magnetization process which can be attributed to the difference in the magnetic properties of two coexisting phases with B2 and L2₁ structural ordering.

Abstract: Surface properties of nanoscale iron garnet films of different compositions prepared by reactive ion beam sputtering were examined by means of scanning probe microscopy. Atomic force microscope images of the film surfaces are represented for the films of different compositions and deposition times. The article presents the dependences of the roughness parameters on the film composition and thickness and on the energy of Ar⁺ ions by which the substrates were pre-treated. It was shown that the roughness parameters of the films' surface increase with the increase of Ar⁺ ions energy and the films' thickness.

Abstract: The ferromagnetic and spin-wave resonance in the electroless deposited thin films of Fe-Ni alloy including alloy with invar content are studied. The dependences of resonance field on the number of mode extracted from spin-wave resonance spectra are deviated from the Kittel dispersion relation. The type and the size of magnetic heterogeneity are estimated in accordance with the spin-wave spectroscopy technique.