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Skokowe zmiany przewodności elektrycznej zostały zaobserwowane w nanozłączach formowanych dynamicznie, pomiędzy ostrzem ze złota a wielowarstwową nanostrukturą magnetyczną (Ni₈₀Fe₂₀/Au/Co/Au) (sub)N. Korzystając z histogramów przewodności wykazano, że warstwy ferromagnetyczne nie modyfikują transportu elektronów przez nanozłącze, odbywa się on w sposób charakterystyczny dla nanozłączy ze złota. Magnetyczna struktura domenowa zoslała zobrazowana za pomocą mikroskopu sił magnetycznych (MFM). Przedstawiono rozkład domen dla dwóch grubości warstw kobaltu (1,4 nm oraz 0,8 nm). Wielkości domen dla tych warstw zależą od kierunku spontanicznego namagnesowania w warstwie Co.
Conductance steps were observed in nanocontacts formed dynamically between gold tip and magnetic multilayer nanostructures (Ni₈₀Fe₂₀/Au/Co/Au) (sub)N. It was shown that ferromagnetic layers do not modify electronics transport in nanocontacts, it occurs the manner characteristic for gold nanocontacts. Magnetic domain structure was investigated by means of magnetic force microscope (MFM). For cobalt layers of thickness 1.4 nm and 0.8 nm domain distribution was shown. Domain size depends on the direction of the spontaneous magnetization vector in Co layer.
Resistivity, temperature coefficient of resistance and magnetization as functions of iron thickness have been studied in a series of magnetron sputtered Fe/Si multilayers with constant Si layer thickness. At the Fe/Si interfaces, a significant amount of deposited iron is transformed into nonmagnetic (0.5 nm) and ferromagnetic (up to 2 nm) nonuniform Fe-Si mixture with a gradient of Fe concentration. Finally, for iron thicknesses above 2.5 nm a bcc-Fe phase appears.
Content available remote Magnetic and magnetoresistive properties of CoFe/Au/Co/Au multilayered structures
Sputter deposited (Co90Fe10 tCoFe/Au 2.7nm/Co 0.6nm/Au 2.7nm)10 multilayers with tCoFe in the 0.4-3.0 nm range were investigated. Magnetic reversal M(H) and magnetoresitance R(H) curves were measured. For tCoFe ??1.2 nm, the R(H) characteristics are similar to that of the prototype system (NiFe/Au/Co/Au), i.e. the system characterized by alternating in plane (NiFe) and out-of-plane (Co) magnetic anisotropy. However, for smaller tCoFe, the effective anisotropy of CoFe layers switches from the in-plane anisotropy to the perpendicular one. This transition is a reason of a strong decrease of the GMR amplitude for tCoFe 1.2 nm. The relatively large values of GMR amplitude (? 7%) and saturation field (900 kA/m) were obtained for sample with tCoFe = 3 nm, measured in perpendicular field configuration. The result indicates a distinct improvement of parameters important for application of studied films as magnetoresistive sensors characterized by the linear R(H) dependence in a broad range of magnetic field.
Content available remote The influence of Ge on antiferromagnetic coupling in Fe/Si multilayers
The magnetic and structural properties of sputtered Fe/Ge, Fe/Ge/Si/Ge and Fe/Si/Ge/Si multilayers were studied. Magnetization measurements revealed the absence of antiferromagnetic coupling for Ge spacer. It was found that during the multilayer deposition a 0.5 nm thick Fe layer at each Fe/Ge interface became nonferromagnetic leading to formation of antiferromagnetic structures. Mössbauer spectra showed the existance of ferro- and/or antiferromagnetic structures at Fe/Ge interfaces, and ferromagnetic and paramagnetic structures at Fe/Si interfaces. We have found that substitution of Si by at least 0.5 nm of Ge in the 1.1 nm thick Si spacer led to disappearance of antiferromagnetic coupling in the Fe/Si multilayers.
Content available remote Temperature dependence of magnetization reversal in Ni80Fe20/Au/Co/Au multilayers
In this contribution we present the results concerning temperature changes of magnetic properties of [Ni80Fe20(2 nm)/Au(tAu)/Co(tCo)/Au(tAu)]10 multilayers (MLs) with tAu = 1.5, 2.2 nm and tCo = 0.6, 0.8 nm. Hysteresis loops of investigated MLs were measured using vibrating sample magnetometer in temperature range from 175 to 423 K. Saturation field HSCo of Co layers, determined from the loops taken with in-plane applied field, increases with decreasing temperature. The HSCo field is directly related to perpendicular magnetic anisotropy of Co layer. It was also found that a shape of a central part of the hysteresis loops, taken with magnetic field applied perpendicular to the sample plane, is characteristic for samples with large perpendicular anisotropy and stripe domain structure. The shape of hysteresis loops is preserved in the whole temperature range of measurements indicating a presence of stable stripe domains. The magnetization reversal of the Co layers can be described by nucleation HN, annihilation HA and coercive HC fields. Temperature dependence of above mentioned parameters is presented.
Content available remote Structure and electronic properties of Fe-Ti thin films
Fe/Ti multilayers (MLs) prepared onto glass substrates using UHV RF/DC magnetron sputtering. Results showed a significant drop of the coercivity measured for the Fe/Ti MLs with decrease in Fe layer thickness - typically from Hc ~ 2.2 kA/m to Hc ~ 0.2 kA/m - observed at a critical Fe thickness dcrit ~ 2.3 nm. Structural studies showed that the deposition of the 0.18 nm - Fe / 0.22 nm - Ti ML at 285 K leads to the formation of an uniform amorphous Fe-Ti alloy thin film due to a strong interdiffusion during the growth process. On the other hand, in-situ annealing of this ML at 750 K for 2 h resulted in the creation of a nanocrystalline phase. Furthermore, in-situ XPS studies showed that the valence band of the nanocrystalline Fe-Ti alloy film is broader compared to that measured for the amorphous phase with the same average composition.
Content available remote Ni80Fe20/Au/Co/Au multilayers as magnetic field sensors
Sputter deposited (Ni80Fe20/Au/Co/Au)N multilayers characterized by alternating easy-plane (Permalloy) and perpendicular (cobalt) anisotropy were investigated. Such films can be used as GMR sensors with linear R(H) dependence in a broad range of magnetic fields. The influence of NiFe, Au, Co layers thickness and repetition number N on GMR effect is discussed. We optimized the multilayer parameters for the application purposes.
Macroscopic description of electronic transport in magnetic layered structures has been extended by including effects due to spin-flip scattering at interfaces. Such processes lead to spin-memory losses at the interfaces and therefore play a significant role in giant magnetoresistance and spin switching phenomena. They also modify distribution of spin currents, electric fields and spin accumulation in the vicinity of interfaces. A system consisting of two oppositely magnetized semi-infinite ferromagnets, and the case of magnetic/nonmagnetic superlattices in parallel and anti-parallel magnetic configurations are analysed in detail.
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