Search

The structural characterization of glass slides surface-modified with 3-azidopropyltrimethoxysilane and used for anchoring nucleic acids, resulting in the so-called DNA microarrays, is presented. Depending on the silanization conditions, the slides were found to show different oligonucleotide binding efficiency, thus, an attempt was made to correlate this efficiency with the structural characteristics of the silane layers. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray reflectometry (XRR) measurements provided information on the surface topography, chemical composition and thickness of the silane films, respectively. The surface for which the best oligonucleotides binding efficiency is observed, has been found to consist of a densely-packed silane layer, decorated with a high-number of additional clusters that are believed to host exposed azide groups.

In granular thin films consisting of small particles of magnetic metal dispersed in nonmagnetic matrix both magnetization and magnetoresistance phenomena are directly related, and their relationship is very complex. This is due to the distribution of ferromagnetic grains in nonmagnetic metallic matrix and its mutual magnetic interactions. In this paper, we studied influence of CoxAg100-x film composition and thickness on film structure, magnetization and magnetoresistance. It has been found that the size of Co grains correlates with the sample thickness for the films with d = 20 nm, and the superparamagnetic state of Co granules is preserved up to x ≤ 55 at.%. However, thicker samples are superparamagnetic only up to x

The influence of the composition of alloy thin films based on Co and Cu on their structural-phase state, electrophysical and magnetotransport properties is presented. The studies were performed for non-annealed and annealed (up to Tmax = 800 K) alloy thin films based on Co and Cu with a thickness of 40 nm, in a wide range of cobalt atomic fractions (0.20 ≤ x ≤ 0.75). For alloy thin films with x ≤ 0.42, thermal treatment in the temperature range from 300 to 800 K for 30 min caused an increase in the value of the giant magnetoresistance (GMR) and coercivity due to the increase in the size of the hcp-Co granules. The highest amplitude of GMR were found in alloys thin films with a total atomic fraction of Co at x = 0.32. The calculation of the thermal coefficient of resistance of alloys showed a qualitative agreement with experiment results for alloy thin films with a total atomic fraction Co x ≤ 0.32.

We investigated structural-phase state, magnetic and magnetoresistive properties in as-deposited CoxAg100-x thin film alloys with a thickness of 35 nm as a function of composition (20 ≤ x ≤ 80 at.%). The aim of this work was to obtain a granular thin film alloy CoxAg100-x with the maximum amplitude of the giant magnetoresistance (GMR) and study of the magnetic field effect on structural characteristics of its surface. Studies of the effect of the magnetic field on the structural characteristics of the surface of the granular thin film alloy Co39Ag61, that characterized by the highest amplitude of GMR at room temperature, were performed. The GMR value for this sample was 14.7 % in transverse and 13.6 % in longitudinal measurement geometries under the magnetic field Bmax = 1.5 T. The application of the magnetic field led to a decrease in arithmetic mean Ra and the root mean square Rq values of the surface roughness, as well as the structural entropy of the system. At the first application of the magnetic field, the greatest decrease in the roughness of Ra by 19 % and Rq by 16 %, respectively, was observed. These changes persisted with increasing field strength up to B = 0.1 T. During the relaxation process (18 hours after the field was switched off), the structural characteristics of the sample were permanent.

We present measurements of magnetic, transport and electronic properties obtained for polycrystalline CeNi2Al3 intermetallic compound. Magnetic susceptibility χ(T) was investigated in the range from 2 to 700 K, and its behavior is characteristic of a compound with unstable valence, varying between Ce3+ and Ce4+. In the temperature range down to 2 K there was no trace of magnetic order, no anomalies in the temperature dependence of the specific heat were found. The Sommerfeld coefficient extracted from the linear term of the heat capacity takes a value of γ = 21 mJ/(mol K2). The dependence of S(T) is linear up to about 25 K, which is symptomatic of a thermopower in the Fermi's liquid regime. The structure of satellites in the Ce(3d) electron spectrum obtained by the X-ray photoelectron spectroscopy (XPS) method indicates that the states of Ce(4f) are of mixed valence character. Analysis of Ce(3d) states based on Gunnarsson-Schonhammer theory shows that the energy of hybridization of Ce(4f) states with a conduction band is about 78 meV. For more detailed information about electronic states the fully relativistic band structure was calculated within the density functional theory (DFT) for the first time. Below Fermi's energy, the density of states is mainly formed by Ni(3d) states hybridized with Ce(4f) ones.

Extensive investigations into structural, magnetotransport and magnetic properties of granular thin films with a thickness of 20 nm based on Co and Ag in a wide range of component concentrations were carried out: 17 ≤ x ≤ 89 where x is at.% of Co. The samples were obtained by the method of electron beam co-evaporation using two independent electron guns at room temperature. The correlation between the structural-phase state and magnetotransport and magnetic properties was established by TEM method. The threshold of structural percolation in granular films was observed for x ≈ 60%. At lower concentration x 70%) the films demonstrated anisotropic magnetoresistance (AMR), which was assumed to be associated with the appearance of ferromagnetic interactions between the cobalt granules.

Few-nanometers-thick Fe3O4(111) films were epitaxially grown on Pt(111) and Ru(0001) single crystal supports by sequential iron deposition and oxidation in an ultra-high vacuum chamber. The growth of well-ordered magnetite films was confirmed by low energy electron diffraction. The films were covered with a protective Au layer and subjected to magnetic and structural studies in ambient conditions. Magnetic hysteresis loops, recorded using magneto-optical Kerr effect apparatus, confirmed magnetic ordering in both films at room temperature. The Kerr measurements indicated in-plane orientation of magnetization, which was supported by the lack of magnetic contrast in magnetic force microscopy images. Atomic force microscopy revealed significant differences in morphology of the films, tentatively attributed to different lattice mismatch with Pt(111) and Ru(0001) single crystal supports.

Temperature-dependent Raman spectroscopy was used for studying few-nanometers-thick epitaxial Fe3O4(111) films grown on Pt(111) and Ru(0001) single crystal supports. The changes in position, intensity and full width at half maximum of the magnetite's A1g peak, corresponding to symmetric stretching of oxygen atoms along Fe–O bonds, were monitored in temperatures ranging from 300 to 80 K. The results gave indications of the presence of the Verwey transition in magnetite films on both supports.

A Co zigzag nanocolumn sample was grown by glancing angle deposition using molecular beam epitaxy. A structural study was carried out using scanning electron microscopy and the magnetic properties and the magnetoresistance were investigated at room temperature. Each zigzag consisted of six arms tilted with respect to each other by approx. 60°, had a club-like shape, diameter in the range of 20–100 nm, a single arm length of about 150 nm and a total height of approx. 370 nm. The magnetization hard axis was observed for the magnetic field oriented parallel to the zigzag long axis and the easy axis for the field oriented perpendicular to the long axis. The system exhibited very high maximum coercivity values, which could find potential applications. The angular dependences of the coercive field and the remanent to saturation magnetization ratio, as well as magnetoresistance curves, indicated the presence of curling magnetization reversal mode.

Composites of unmodified or oxidized carbon nano-onions (CNOs/ox-CNOs) with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are prepared with different compositions. By varying the ratio of PEDOT:PSS relative to CNOs, CNO/PEDOT:PSS composites with various PEDOT:PSS loadings are obtained and the corresponding film properties are studied as a function of the polymer. X-ray photoelectron spectroscopy characterization is performed for pristine and ox-CNO samples. The composites are characterized by scanning and transmission electron microscopy and differential scanning calorimetry studies. The electrochemical properties of the nanocomposites are determined and compared. Doping the composites with carbon nanostructures significantly increases their mechanical and electrochemical stabilities. A comparison of the results shows that CNOs dispersed in the polymer matrices increase the capacitance of the CNO/PEDOT:PSS and ox-CNO/PEDOT:PSS composites.

We review selected results concerning the interlayer exchange coupling in Fe/SixFe1−x , Fe/Ge and Co/Si layered structures. Among the ferromagnet/semiconductor systems, Fe/Si structures are the most popular owing to their strong antiferromagnetic interlayer coupling. We show that such interaction depends not only on semiconducting sublayer thickness, but also on deposition techniques and on the chemical composition of the sublayer as well. In similar heterostructures e.g. Fe/Ge, antiferromagnetic coupling was observed only in ion-beam deposited trilayers at low temperatures. In contrast, in Fe/Ge multilayers deposited by sputtering, no such coupling was found. However, when the Ge is partially substituted by Si, antiferromagnetic interlayer coupling appears. For Co/Si multilayers, we observed a very weak exchange coupling and its oscillatory behavior. The growth of Co on Si occurs in an island growth mode. The evolution of magnetic loop shapes can be successfully explained by the interplay between interlayer coupling and anisotropy terms.

A direct comparison between the Hall effects and giant magnetoresistance of ferromagnetic multilayers of similar composition (Ni80Fe20/Au/Co/Au)N with alternating in-plane and out-of-plane magnetization direction of Co layers is presented. The characteristic features at magnetic field-dependence of giant magnetoresistance were correlated with the creation and annihilation of the stripe domains in Co layer, with perpendicular anisotropy. The nucleation field values were investigated as an Au layer thickness function. Furthermore, the in situ conductance measurement results characterised the island growth mode of the ferromagnetic layers. The percolation thicknesses were also indicated.

In this paper we study Fe/Si and Fe/Ge multilayers prepared at room temperature by magnetron sputtering. In situ conductance measurements reveal the formation of interfacial Fe–Si and Fe–Ge mixtures. During the Fe deposition a modification of growth mode is noticed. Deposition of Si (or Ge) onto Fe leads to the reduction of the Fe layer thickness due to interdiffusion, and Fe–Si (or Fe–Ge) structures appear. Above about 1.3 nm of deposited Si (1.5 nm of Ge) nominally pure Si (Ge) starts growing. Surface topography of the Fe/Si multilayers is studied by atomic force microscopy.

The antiferromagnetically coupled Fe/Si x Fe 1-x multilayers deposited in UHV by magnetron sputtering onto oxidized Si wafers for different Fe layer thicknesses 0.3 nm

Sputtered Ni 80 Fe 20 /Au/Co/Au multilayers (MLs) exhibit perpendicular anisotropy of Co layers and easy-plane anisotropy of Permalloy layers. In these samples the changes of relative orientation of magnetization between Co and NiFe layers, with magnetic field, can be determined by magnetoresistance measurements. The magnetic structure is discussed for two types of Ni 80 Fe 20 /Au/Co/Au MLs characterized by a weak coupling between ferromagnetic layers: (i) MLs with rectangular hysteresis loops and small coercive field, (ii) MLs with dense stripe domain structure in Co layers.

The antiferromagnetically coupled Fe/Si multilayers deposited by magnetron sputtering with different Fe layer thicknesses have been examined. It has been shown that the magnetization of ferromagnetic layer reduces its value with decreasing Fe layers thickness affecting the antiferromagnetic interlayer coupling. This coupling has been found to occur for Fe layer thicker than 0.5 nm. It has been shown that the antiferromagnetic interlayer coupling occurs through the semiconducting spacer layer. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Thin oxide films epitaxially grown on metal single crystal surfaces may exhibit structural properties that differ from the corresponding bulk oxide materials. The structure of the films is often rendered by their thickness, the structure and properties of the substrate and by the nature of the oxide/substrate interface. We prepared thin iron oxide films on Pt(111) and Ru(0001) and studied their structure using STM, LEED and XPS. The structure of FeO(111) – the iron oxide phase that forms at the interface with the metal single crystal – depends on the parameters of the support and is believed to further influence the structure of thicker iron oxide films, such as Fe3O4(111), that are being grown on top of it. In this article we discuss the role of one of the important parameters that may determine this structure – the epitaxial strain at the iron oxide/metal single crystal interface.

34th International School on the Physics of Semiconducting Compounds, Jaszowiec, POLAND, JUN 04-10, 2005; International audience; Structures containing magnetic metallic layers attract a lot of attention because of their possible applications in the area of spintronics. The hybrid structures compatible with the Si crystal lattice parameter are of special interest. In this work the short-period Fe/Si multilayers were grown by the sputtering onto (001)-oriented Si substrate and investigated by various techniques. After the deposition, all multilayers were characterized by atomic force microscopy. The goal of the present paper was to determine the chemical composition of thin layer created at the interface in Fe/Si multilayers due to the Fe diffusion into Si, as well as to analyse the phenomena, which take place in this area. The results of the optical characterization by the Raman scattering were correlated with the magnetic properties of investigated structures (determined by means of the Kerr rotation).

The structural and magnetic properties of Fe/Si x Fe 1− x multilayers (Mls) have been studied by the conversion electron Mossbauer spectroscopy (CEMS) and magnetic measurements. We believe that the Fe-Si silicides responsible for the AF coupling in Fe/Si multilayers are semiconducting Si x Fe 1− x phases rich in Si which appear in inhomogeneous spacer layer. Antiferromagnetically coupled Fe/Si multilayers have been successfully applied as artificial antiferromagnets in the magnetoresistive (Fe/Si) 15 /Fe/Co1/Cu/Co2 pseudo-spin-valve system.

The influence of Ar-ion irradiation on the microstructure, interlayer coupling and giant magnetoresistance (GMR) effect in the model Fe/Cr system was studied by the conversion electron Mossbauer spectrometry (CEMS), vibrating sample magnetometry (VSM), and magnetoresistivity, for the Fe-1.4 nm/Cr- t Cr multilayers with t Cr ranging from 0.73 to 1.85 nm. The loss of antiferromagnetic coupling and the simultaneous degradation of GMR, observed for increasing ion dose, was caused by the formation of pinholes due to the increase of interface roughness and at high ion doses, by the ion-beam mixing leading to the alloying of Fe and Cr at interfaces.

The Fe/SixFe100-x and Co/Si multilayers have been examined. The strongest antiferromagnetic interlayer coupling, J = -1.94 mJ/m(2), was found in Fe/SixFe100-x multilayers for x = 100. The analysis of the temperature dependences of remanence to saturation magnetization ratios allowed to find the value of semiconductor spacer layer energy gap (E-g approximate to 200 meV) of the examined structures. It suggests that the Fe-Si phase, responsible for antiferromagnetic coupling is an amorphous-like Fe-Si phase. For Co/Si multilayers a very weak exchange coupling and its oscillatory behavior was observed. It was shown that the growth of the Co on Si occurs in an island growth mode. The evolution of magnetic loop shapes can be successfully explained by the interplay between interlayer coupling and anisotropy terms. (C) 2004 Elsevier B.V. All rights reserved.

The magnetic properties of sputtered (Ni_(83)Fe_(17)/Au/Co/Au) multilayers with various thicknesses of Au (0.5 ≤ t_(Au) ≤ 3 ㎚), Ni-Fe (1 ≤ t_(Ni-Fe) ≤ 4 ㎚) and Co (0.2 ≤ t_(Co) ≤ 1.5 ㎚) layers were characterized. An alternating inplane and out-of-plane anisotropy of the ferromagnetic layers was achieved for the structures (t_(Au)≥ 1.5 ㎚) showing a weak coupling between the Ni-Fe layers with an in-plane anisotropy and the Co layers (0.3 ≤ t_(Co) ≤ 1.2 ㎚) with a perpendicular anisotropy. For such a structure, a detailed discussion on the GMR effect is presented, relating to the magnetization reversal from a mutually perpendicular magnetic configuration at the remanence to a parallel one at the saturation. An influence of the dense labyrinth domain structure on the magnetoresistance effect is also addressed.

The magnetic properties of the sputter-deposited Cu/NiFe/MnIr/CoFe/Al+Ox/NiFe/Ta system are investigated to create a magnetically optimized TMR system and to tailor the magnetic properties. The unidirectional exchange anisotropy was found to depend strongly on the MnIr layer thickness with no exchange bias for t(MnIr) less than or equal to 5 nm and decreasing bias for t(MnIr) greater than or equal to 10 rim. For t(MnIr) = 15 nm exchange coupling energy was found to be 0.17 mJ/m(2) and the blocking temperature reaches 500 K. The thickness of the CoFe layer was found to strongly influence the shift of the magnetization loop of the upper NiFe layer by magnetostatic coupling. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The magnetoresistive properties of sputtered spin-valve-like Co(t Co1 )/Cu/Co(t Co2 ) multilayers with alternating thicknesses of Co sublayers are investigated. It is shown that annealing at temperatures up to 573 K enhances a magnetoresistance ratio but does not reduce a hysterecity of a R(H) dependence. It is also shown that multilayers with thinner Co sublayers are relatively more stable at higher annealing temperatures.

An advanced deposition technique known as glancing angle deposition was used to fabricate randomly seeded magnetic cobalt columnar nanostructures. The existence of nanocolumns was con rmed by the cross-section scanning electron microscopy. The evolution in the magnetization reversal mechanism as a function of the lm thickness was investigated. The coercivity HC and MR/MS ratio (where MR and MS denote the remanent and saturation magnetization, respectively), derived from the magnetic hysteresis loops, are discussed as a function of the angle between the external magnetic eld and the surface normal. The direction of the magnetization easy/ hard axis and the columns inclination angle were determined on the basis of the angular dependences of the HC and the MR/MS. A crossover from the coherent rotation, based on the Stoner Wohlfarth model, to the curling reversal mode was observed.

Pseudo-spin-valves (PSV) structures, Ni83Fe17-3 nm / Co-2.5 nm / Au-tAu / Co-2.5 nm, with 2.4≤tAu≤3.2 nm were deposited by UHV magnetron sputtering. The weak ferromagnetic coupling J≈2×10-6 J/m2 between Ni-Fe/Co and Co layers and GMR effect ≈ 3% was found at RT. The GMR amplitude decreases monotonically from 5% at -100°C to 1% at 200°C. However, the slope of R(H) curve, i.e., GMR field sensitivity, is equal to about 1.5%/Oe and remains almost constant in the entire investigated temperature range. Additionally, our PSV display a good thermal stability, with no significant changes of magnetic and transport properties after annealing up to 250°C.

The interlayer exchange coupling and GMR effect of (permalloy/Cu x Au1-x )30 (Py = Ni83Fe17; 0.29≤x≤0.75) sputtered multilayers (MLs) were investigated. The strength of the antiferromagnetic (AF) interlayer coupling J AF was determined from M(H) and/or R(H) curves. GMR effect and AF coupling was found in entire investigated concentration range of Cu x Au1-x . For x0.65 J AF increased to a value characteristic of Py/Cu MLs (J AF≈10-5 J/m2). The second maximum of AF coupling (J AF≈10-7 J/m2) was only found for x≈0.75 at t Cu-Au≈2.6 nm.

The influence of annealing on giant magnetoresistance (GMR) effect and magnetization reversal processes has been investigated in Py/Cu (Py = Ni 83 Fe 17 ) sputter-deposited multilayers (MLs) with a limited number of magnetic sublayers (N ≤ 6) and equal sublayer thicknesses both for Py and Cu (t Cu = 2 nm, t Py = 2 nm). Based on the magnetization and magnetoresistance measurements it has been shown that the magnetic behavior of such MLs is strongly influenced by annealing driven disruption of magnetic layers (lateral decoupling) and nonmagnetic layers (magnetic bridging between Py layers). A comparison of experimental hysteresis curves with model dependences indicates that annealing causes a change of the magnetization reversal from a local to an absolute energy minimum mode leading to quasi-two-state magnetoresistance characteristics.

In the following we present the role of surface scattering at Au/Co and Au/Ni–Fe interfaces in Ni–Fe/Au/Co/Au multilayers deposited in different temperatures. Specularity parameter, which describes the electron scattering, is calculated from fitting in situ collected conductance data with the Fuchs–Namba– Tesanovic model. Application of the parallel resistors model enabled to depict changes between Au/Co and Au/Ni–Fe interfaces within multilayers for each repetition. The correlation between enhanced grain boundary scattering for higher deposition temperatures and surface roughness of Ni–Fe/Au/Co/Au multilayers is found.

The asymmetric GMR field dependencies at room temperature were observed in (Ni 83 Fe 17 =Py)/Cu multilayers deposited by sputtering. The appearance of giant magnetoresistance (GMR(H)) asymmetry is related to the existence of superparamagnetic entities located at the vicinity of the Py/Cu interfaces. It is shown that the presence of an external magnetic field can reduce the scattering of the conduction electrons, by fluctuating superparamagnetic moments leading to the occurrence of an extra contribution to the GMR effect. The amount of asymmetry observed in the magnetic field dependencies of the GMR effect depends both on the value of the external magnetic field as well as on its sweeping rate. It reflects the importance of the interfacial magnetic states and their influence on the GMR effect observed in multilayered structures.

The field dependencies of resistance and magnetic moment of the Co/Cu multilayers manifesting the GMR effect have been simultaneously examined in situ, during deposition process. The combination of these measurements with in situ thickness dependent resistance measurements allowed us to interpret the changes of the magnetic hysteresis loops. It has been shown that the all measured quantities can be presumably affected by the surface anisotropy. (C) 1999 Elsevier Science B.V. All rights reserved.

The influence of germanium on antiferromagnetic (AF) exchange coupling in sputtered Fe/Si multilayers has been examined with the use of magnetic moment, Hall effect and Mossbauer spectroscopy measurements. We have found that substitution of Si by Ge led to a gradual vanishing of AF coupling depending not only on the thickness of the spacer layer that is composed of Si and Ge layers but also on interfacial mixing occurring between Fe and Si(Ge) layers during deposition process.

The coupling between permalloy and cobalt layers (characterized by in-plane and perpendicular anisotropy, respectively) in NiFe/Au/Co/Au sandwich films and multilayers was investigated. In sandwich samples the main contribution to the effective coupling comes from the structural imperfections (pinholes and interface roughness). For multilayers, due to creation of dense stripe domains in Co layers, the supplementary coupling is observed in the field range defined by the nucleation and annihilation of the domains.

The Fe–Cu layers were produced by the Impulse Plasma Deposition method in two impulse plasma coaxial accelerators. Each of them was equipped with an internal electrode made of Fe or Cu, which functioned as the source of the alloying components of the layer material. This study shows the relation between the phase structure and the magnetoresistance values. A small value of magnetoresistance was measured in layers directly after deposition process. The magnitude of the effect increased after the 1 h annealing in 600 K.

The investigation of thermal stability of sputtered permalloy/copper multilayers with various Cu sublayer thicknesses was performed. The observed changes of antiferromagnetically coupled fraction of multilayers, their magnetoresistance, and shape of the hysteresis loop with increasing annealing temperature are, in our opinion, a consequence of grain boundary diffusion creating the magnetic bridges (pinholes) across the Cu sublayer. It is demonstrated that the high sensitive giant magnetoresistance observed for permalloy/copper multilayers with Cu sublayer thickness equal to about 2 nm is not destroyed by annealing at temperatures up to 175°C.

In multilayered thin films consisting of permalloy (Ni80Fe20) and copper, a strong antiferromagnetic coupling and a related giant magnetoresistance can be found which oscillates with the thickness of the copper spacer layers. This, however, is usually detected only in sputtered films, whereas evaporated multilayers often show no or only a very weak coupling and giant magnetoresistance. Here, we report on a comparative study of sputtered and evaporated multilayers. In the first maximum of the antiferromagnetic coupling, i.e. at a copper thickness of 0.9 nm, our sputtered films exhibit a saturation field of up to 1000 Oe and values of the giant magnetoresistance of up to 22% at room temperature at a permalloy thickness of about 2 nm. In contrast to this, the corresponding evaporated multilayers do not show any sign of antiferromagnetic coupling. A subsequent analysis of the films by cross-sectional transmission electron microscopy imaging indicates, in small regions, a good and a poor multilayered structure for sputtered and evaporated films, respectively. X-ray reflectivity measurements and atomic force imaging of the surfaces pointed to an increased interface roughness in the evaporated films. Thus we conclude that the absence of the antiferromagnetic coupling in the evaporated films should be related to an increased roughness of the layer interface and not to interdiffusion. (C) 1998 Elsevier Science B.V. All rights reserved.

Ferromagnetic resonance has been applied to study sputtered $[\mathrm{P}\mathrm{e}\mathrm{r}\mathrm{m}\mathrm{a}\mathrm{l}\mathrm{l}\mathrm{o}\mathrm{y}/\mathrm{C}\mathrm{u}{]}_{100}$ multilayers with Permalloy (Py) and Cu layers thicknesses $5 \AA{}l{d}_{\mathrm{Py} }l 40 \AA{}$ and $8 \AA{}l{d}_{\mathrm{Cu}}l 40 $, respectively. The effective magnetization is analyzed in the vicinity of nominal critical thicknesses of Py layers, $2\ensuremath{\Delta}d = 4.9$, 7.6, and 8.3 \AA{}, at 77, 293, and 400 K, respectively. From its behavior and the temperature measurements of ferromagnetic resonance (FMR) spectra we argue about the magnetic structure of a statistically averaged interface between Py and Cu: At room temperature, about 0.5 monolayer (ML) (1 ML = 1.8 \AA{}) may be magnetically inactive due to spin wave excitations in ultrathin films and about 1.5--2 monolayers---due to intermixing resulting from roughness. Trapezoidal-like magnetization profiles in ultrathin Py layers 4--7 monolayers thick are discussed in terms of percolation of magnetic clusters within a rough interface. The FMR linewidth depends on the thickness of Py layer as ${d}_{\mathrm{Py}}^{\ensuremath{-}2}$.

It has been shown that in Py/Cu (Py = Ni 87 Fe 17 , permalloy) multilayers obtained by face-to-face sputtering technology, two well-separated antiferromagnetically coupled ranges can be found centered at d Cu ≈ 1 and 2 nm, respectively. However, d Cu values corresponding to the largest field sensitivity of the GMR effect are different from those for which the strongest antiferromagnetic exchange coupling has been found. With decreasing Py thickness, the magnetic properties become strongly influenced by the magnetisation fluctuations. We attribute this effect to the presence of compositionally intermixed interfaces. Changes in the magnetic properties and magnetoresistance as a function of Py thickness are analysed in terms of evolution from paramagnetic through superparamagnetic to ferromagnetic behaviour of these intermixed regions.

The as-deposited and annealed Co/Ag discontinuous multilayer-like structures obtained by the dc facing sputtering method have been examined. The most characteristic feature observed in these heterogeneous structures is the absence of any magnetoresistance-magnetisation correlation. Discontinuous Co sublayers are thought to consist of fine superparamagnetic and ferromagnetic grains. However, the superparamagnetic grains with bimodal size distribution have previously been shown to be responsible for the field dependence of GMR. Using the bimodal superparamagnetic grain distribution the GMR(H) dependences have been successfully modelled with the use of two Lange-vin functions simulating the magnetisations of the superparamagnetic grains.

We report structural and magnetic properties of Ni83Fe17/Cu multilayer films with various buffer layer and sublayer thicknesses of copper dcu and Permalloy dp y deposited by face-to-face sputtering. The following features prove a good quality of our films: a well-layered structure, complete antiferromagnetic coupling with a low coupling strength (2 x 10 -5 J/m2 for dcu = 1 nm and 10 -5 J/m2 for dc" = 2.1 nm) and a low coercive field which make them attractive for possible applications as giant magnetoresistance sensors.

The as-deposited and annealed Co/Ag discontinuous multilayer-like structures were examined. Discontinuous Co sublayers are thought to consist of fine superparamagnetic and ferromagnetic grains. Using the bimodal superparamagnetic grain sizes distribution the GMR(H) dependencies were successfully modelled with the use of two Langevin functions simulating the magnetization of the superparamagnetic grains.

The magnetic and structural properties of Fe/Si multilayers (Mls) have been studied by x-ray diffraction (XRD) and conversion electron Mossbauer spectroscopy (CEMS) methods. Strong antiferromagnetic (AF) coupling J=-1.93 mJ/m(2) accompanied by saturation field of 1.5 T has been found for Si layer thickness d(Si)=1.4 nm. Magnetic moment measurements of Fe/Si Mls vs Fe thickness revealed that 0.25 nm of Fe per single interface is magnetically inactive. The CEMS spectra recorded at room temperature consist of the Zeeman sextet characteristic of the pure Fe phase (hyperfine field of about 32.8 T) accompanied by two spectral components related to FeSi system: magnetic broad sextet and a quadrupole doublet. The broad sextet could originate from various Fe sites at the interface. The nonmagnetic quadrupole split (QS) doublet is most probably associated with the nonstoichiometric c-Fe1-xSix phase. For larger Si layer thickness (d(Si)>2 nm) the spectral contribution of the QS doublet increases from 5.7% to about 16%. (C) 2003 American Institute of Physics.

We review selected results concerning the interlayer exchange coupling in Fe/SixFe1−x, Fe/Ge and Co/Si layered structures. Among the ferromagnet/semiconductor systems, Fe/Si structures are the most popular owing to their strong antiferromagnetic interlayer coupling. We show that such interaction depends not only on semiconducting sublayer thickness, but also on deposition techniques and on the chemical composition of the sublayer as well. In similar heterostructures e.g. Fe/Ge, antiferromagnetic coupling was observed only in ion-beam deposited trilayers at low temperatures. In contrast, in Fe/Ge multilayers deposited by sputtering, no such coupling was found. However, when the Ge is partially substituted by Si, antiferromagnetic interlayer coupling appears. For Co/Si multilayers, we observed a very weak exchange coupling and its oscillatory behavior. The growth of Co on Si occurs in an island growth mode. The evolution of magnetic loop shapes can be successfully explained by the interplay between interlayer coupling and anisotropy terms.

The temperature dependence of the spontaneous Hall R s ( T ) and Nernst-Ettingshausen Q s ( T ) coefficients of amorphous Co-Ti thin films has been studied. It was found that the spontaneous Hall effect was due to side-jump mechanism and the R s ( T ) dependence arose from the magnetic and phonon contribution to the resistivity. The spontaneous Nernst-Ettingshausen coefficient is discused applying the Kondorskii and Berger formula Q = −T(α + βϱ). An attempt to find a suitable explanation of our Q s ( T ) results reveals that the scattering mechanism responsible for the observed Q s ( T ) behaviour are mainly the phonon and spin-disorder scattering although the latter plays an important role.

The structure and magnetic properties of thin Fe90–xNixZr10 alloy films with x = 0, 5, and 10 are studied. The structure observed by electron diffraction and transmission electron microscopy reveals the crystalline phase in as-deposited samples. However, the temperature dependence of resistivity suggests the presence of a significant amount of amorphous phase as well. Some new fine-grained structure is observed in the studied films after annealing. Saturation magnetization and magnetization reversal curves are obtained by the Hall effect, and magnetooptical Faraday and Kerr effects, respectively. Ms depends significantly on the alloy composition and weakly on the heat treatment condtions. Hysteresis loops of the films studied reveal very weak uniaxial in-plane anisotropy and undirection-like anisotropy, the latter leading to asymmetric loops shifted along the H-axis. The magnetic properties appear to be consistent with the structure of the studied samples.

The resistivity (p) and temperature coefficient of resistivity (TCR) dependencies on modulation wavelength (a) were examined in Fe/Zr multilayer thin films. It was shown that the p()) and TCR(λ) behaviours can be explained on the basis of the assumption that the amorphous phase can be spontaneously formed during the deposition process. We found that the effective thickness of the amorphous phase was =2 nm per single interface. PACS numbers: 75.50.—y

Magnetisation reversal and magnetoresistance of sputtered Ni 83 Fe 17 /Au/Co/Au multilayers with Co layer thicknesses 0.2⩽ t Co ⩽1.5 nm were studied. Depending on t Co , the Co layers are superparamagnetic ( t Co t Co t Co ⩾0.6 nm) layer structure and, for t Co ⩽1.2 nm, show perpendicular anisotropy.