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We derive four reduced two-dimensional models that describe, at different spatial scales, the micromagnetics of ultrathin ferromagnetic materials of finite spatial extent featuring perpendicular magnetic anisotropy and interfacial Dzyaloshinskii–Moriya interaction. Starting with a microscopic model that regularizes the stray field near the material's lateral edges, we carry out an asymptotic analysis of the energy by means of Γ -convergence. Depending on the scaling assumptions on the size of the material domain versus the strength of dipolar interaction, we obtain a hierarchy of the limit energies that exhibit progressively stronger stray field effects of the material edges. These limit energies feature, respectively, a renormalization of the out-of-plane anisotropy, an additional local boundary penalty term forcing out-of-plane alignment of the magnetization at the edge, a pinned magnetization at the edge, and, finally, a pinned magnetization and an additional field-like term that blows up at the edge, as the sample's lateral size is increased. The pinning of the magnetization at the edge restores the topological protection and enables the existence of magnetic skyrmions in bounded samples. [ABSTRACT FROM AUTHOR]

Herein, the experimental observation of micrometer‐scale magnetic skyrmions at room temperature in several Pt/Co‐based thin film heterostructures designed to possess low exchange stiffness, perpendicular magnetic anisotropy, and a modest interfacial Dzyaloshinskii–Moriya interaction (iDMI) is reported. It is found both experimentally and by micromagnetic and analytic modeling that a low exchange stiffness and modest iDMI eliminates the energetic penalty associated with forming domain walls in thin films. When the domain wall energy density approaches negative values, the remanent morphology transitions from a uniform state to labyrinthine stripes. A low exchange stiffness, indicated by a sub‐400 K Curie temperature, is achieved in Pt/Co, Pt/Co/Ni, and Pt/Co/Ni/Re structures by reducing the Co thickness to the ultrathin limit (<0.3 nm). Similar effects occur in thicker Pt/Co/NixCu1−x structures when the Ni layer is alloyed with Cu. At this transition in domain morphology, skyrmion phases are stabilized by small (<1 mT), perpendicular magnetic fields, and skyrmion motion in response to spin–orbit torque is observed. While the temperature and thickness‐induced morphological phase transitions observed are similar to the well‐studied spin reorientation transition that occurs in the ultrathin limit, the underlying energy balances are substantially modified by the presence of an iDMI. [ABSTRACT FROM AUTHOR]

Electric field-controlled ferromagnetism of (Zn,Co)O is demonstrated via anomalous Hall effect measurements. The electron carrier concentration in this material is 1.65x10(20) cm(-3) as measured via ordinary Hall effect at 4 K, and an anomalous Hall effect is observed up to 6 K, but with no hysteresis at any temperature. With positive electric gate field, the carrier concentration is increased by approximately 2%, resulting in a clear magnetic hysteresis at 4 K. The ability to reversibly induceeliminate ferromagnetism by applied gate field alone, measured via the effect on the carriers, is a clear sign of carrier-induced ferromagnetism in this system.

Graphical abstract Highlights • Ferromagnetic and/or antiferromagnetic-like ordering at the (1 1 1) surface in intermetallic compound Ni 3 Ge is discovered, although the magnetization in the bulk material is zero. • In some configurations, the ferromagnetic and anti-ferromagnetic-like states are energetically nearly degenerated. • This finding is crucial when developing materials for new magnetic applications and may be exploited to produce two-state memory cells and switches. Abstract By means of the first-principles calculations we investigate the magnetic properties of four low-index surfaces in the bulk nonmagnetic Ni 3 Ge intermetallic compound with the L1 2 structure. We predict that the (1 1 1) surface of Ni 3 Ge is magnetically ordered, with all magnetic moments located at the Ni sites. Magnetic order is also found at the Ni-terminated (0 0 1), (1 1 0) and (2 1 0) surfaces, however, the nonmagnetic NiGe-terminated surfaces are more stable similarly as in other L1 2 compounds. It turns out that the magnetic order in the bulk Ni 3 Ge is destroyed completely by the hybridization of Ge- p and Ni- d states and it is recovered at some surfaces due to the reduced coordinate number of Ni atoms. We also report on a particular distribution of magnetization at the Ni 3 Ge(1 1 1) surface where the ferromagnetic and anti-ferromagnetic-like states are degenerated because there are magnetically dead layers between the two magnetic surfaces and there is no interference between them. The calculated results obtained for Ni 3 Ge are compared with those for Ni 3 Al; the differences between these two compounds are discussed. [ABSTRACT FROM AUTHOR]

Manganese bismuth thin films were deposited from a Mn55Bi45 (at.%) alloy target onto glass substrates at room temperature using dc magnetron sputtering. The ferromagnetic low-temperature phase (LTP) of MnBi was formed through a subsequent vacuum annealing step. The resulting thin films were highly c-axis textured. Magnetic measurement shows a maximum saturation magnetization of 600 emu/cm3 (0.60 MA/m). A magnetic uniaxial anisotropy energy density of \sim 1.86 \cdot 10^7 erg/cm3 (~1.86 MJ/m3) was measured by torque magnetometry. The coercive field has a positive temperature coefficient and reaches 12 kOe (1.2 T) and 14 kOe (1.4 T) at 300 K for the out-of-plane and in-plane direction, respectively. Density functional theory calculations have confirmed that the magnetocrystalline anisotropy energy increases with increasing temperature as a result of a spin-reorientation occurring around 100 K. Growing LTP MnBi thin films directly from an alloy Mn55Bi45 target is an important step toward facilitating the synthesis of multilayers for spintronics or in an exchange spring magnet configuration. [ABSTRACT FROM AUTHOR]

New ferromagnetic films with composition SiC x N y Fe z were synthesized using chemical vapor deposition technique. Films were deposited using ferrocene, 1,1,1,3,3,3-hexamethyldisilazane (HMDS) and hydrogen gaseous mixture. Chemical and phase composition of the films were studied by FTIR, Raman spectroscopy and X-ray diffraction with grazing incidence (GI-XRD). FTIR spectra analysis confirmed the existence of Si-C and Si-N bonds. Graphite inclusions and amorphous carbon were determined by Raman spectra analysis. The surface of the SiC x N y Fe z films studied by SEM is covered by nanocrystallites of iron oxide Fe 3 O 4 phase. The main purpose of GI-XRD analysis is to describe the layered structure of the films in detail. It was shown by GI-XRD study, that phase composition of the SiC x N y Fe z films varies from iron oxide Fe 3 O 4 to iron silicide Fe 3 Si and silicon carbide SiC with the deposition temperature growing. It was established, that SiC x N y Fe z films are perspective for application in the spintronic field. [ABSTRACT FROM AUTHOR]

This study reports micro-fabricated magnet and superconductor (permalloy/Pb 82 Bi 18 ) hybrid film structures sequentially grown by magnetron sputtering and thermal deposition techniques. 300 nm thick PbBi film was quench condensed on top of a patterned permalloy film. Permalloy film was sputtered and patterned to form few micrometer-wide stripes. Ferromagnetic and superconducting layers were separated by Al 2 O 3 insulation. Transport superconducting properties, i.e. transition temperature T C ( H ) and second critical field H C 2 ( T ) were measured in a range of applied magnetic field between H = 0 and H = 7 kOe for the hybrid system and a control sample with only a layer of superconducting film deposited. The H C 2 ( T ) data showed that due to the interplay between the superconducting film and the ferromagnet, superconducting (SC) and normal current paths formed on the SC film. [ABSTRACT FROM AUTHOR]

Abstract: Exchange-bias phenomena of ultrathin antiferromagnetic/ferromagnetic bilayers on a semiconductor surface have been experimentally investigated. We demonstrate that 5 monolayers CoO with a face centered cubic structure are sufficient for the occurrence of exchange-bias phenomena for a CoO/Co/Ge(111) system. By increasing the thickness of the CoO layer to 10 monolayers, the increase of the exchange bias field to a maximum value of 0.58kOe is observed and can be attributed to the increasing anisotropy energy of antiferromagnetic layer and the increasing number of pinned uncompensated spins at the interface. The pinning of magnetic moments at the CoO/Co interface results in that 3.6 monolayers Co do not contribute to the magneto-optical responses. However, for a CoO/Co/Ge(100) system, the commencement for exchange bias and the maximum exchange bias field are postponed to larger CoO thicknesses. This is mainly attributed to the discontinuous CoO layer on a disordered Co layer which is formed due to the looseness of the Ge(100) surface. [Copyright &y& Elsevier]

Abstract: Reactive-sputtered epitaxial Ti1− x Cr x N films are ferromagnetic in the range of 0.17⩽ x ⩽0.51 due to the Cr–N–Cr double-exchange interaction below the Curie temperature (TC ). The TC first increases, then decreases as x increases, and a maximum of 120K appears at x =0.47. All of the films are metallic with a transition near TC . A resistivity minimum ρ min is observed below 60K in the films with 0.10⩽ x ⩽0.51 due to the effects of the weak localization and electron–electron interaction. The negative magnetoresistance (MR) is caused by the double-exchange interaction below TC and the weak localization can also contribute to MR below T min where ρ min appears. The x-dependent electron carrier densities reveal that the ferromagnetism is not from the carrier-mediated mechanism. The anomalous Hall resistivity follows the relation of , which is from the side-jump mechanism. [Copyright &y& Elsevier]

Development of (001) texture in FePt thin films deposited on glass substrates with different thickness (t) treated by rapid thermal annealing (RTA) is studied. A critical thickness of 30 nm is characterized: below which the (001) preferred orientation of the films develops with increasing t; when t > 30, the films become isotropic. Remarkable perpendicular anisotropy in magnetic properties is achieved in the 30 nm thick sample with the best (001) texture. Discontinuous changes are also observed in surface morphology, microstructure, magnetic domain structure, and internal stress. Direct evidences are presented relating the formation of (001) texture to abnormal grain growth. The internal stress/strain analysis indicates that the residual tensile (\sigma) stress is proportional to the degree of (001) preferred orientation. A large value of \sigma of about 8.9 GPa is obtained in the film with t = 30, suggesting the driving force forming the texture. [ABSTRACT FROM AUTHOR]

Using temperature-dependent X-ray diffraction and magnetization measurements, a reversible face-centered cubic (fcc) to body-centered cubic (bcc) structural transformation was confirmed in freestanding epitaxially grown films after lift-off from their MgO (100) substrates—a transformation generally considered irreversible in bulk samples. The latter is accompanied by a distinct change of the sample magnetization. In contrast, substrate constraints were found to suppress the thermoelastic fcc to bcc transformation in substrate-attached films. [ABSTRACT FROM AUTHOR]

Abstract: We present a systematic change of the magnetic domain structure with temperature in epitaxial ferromagnetic MnAs film on GaAs (001), observed in a wide temperature range of 15–45°C by magnetic force microscopy. Interestingly, it is found that, as temperature increases, the domain structure within the ferromagnetic α-MnAs stripes shows a mixture of head-on and simple domains at 15°C and then, takes a complete transition to simple ones above 15°C. This change could be understood by change in the demagnetizing factor of the cross-section of the ferromagnetic stripes with temperature. [Copyright &y& Elsevier]

It is found that in laser-induced thermoelectric voltage (LITV) signal in La1-xCaxMnO3 and YBa2Cu3O7-y.H thin films, both the rise-time and decay time are increasing linearly with the total parallel-connected resistance of the load and the film. To obtain fast laser-induced thermoelectric voltage signal, smaller load should be connected in parallel with he film. [ABSTRACT FROM PUBLISHER]

Abstract: We studied the magnetoimpedance (MI) effect of FeCoB(100nm)/Cu(100nm)/FeCoB(100nm) sandwiched films with different thickness of Permalloy as underlayer for the FeCoB ferromagnetic layer. The maximum MI ratio of sandwiched film is 9.2% when the thickness of the Permalloy underlayer is 2–3nm. The improvement of MI ratio of sandwiched films with Permalloy underlayer was explained by exchange induced ripple reduction mechanism. [Copyright &y& Elsevier]

Abstract: Recent theoretical results are highlighted that illustrate some of the interesting phenomena associated with magnetic domain boundary walls. Two problems will be discussed: dynamics associated with domain wall propagation, and effects related to spin transport through domain walls. For the first problem, an example of wall interaction and motion through a random potential will be discussed with reference to the general problem of roughening transitions. Images of domain dynamics in thin films of ion irradiated Co reveal a de-roughening transition associated with long range magnetostatic interactions between pairs of domain walls. A scaling theory of this transition is described in which a curious type of dynamic hysteresis can occur. For the second problem, results from calculations of ballistic charge and spin transport through domain boundary walls are discussed in terms of an effective circuit model. [Copyright &y& Elsevier]

Abstract: Co-doped SnO2 thin films are grown on sapphire (0001) substrates at 600 °C by the technique of dual-beam pulsed laser deposition. The prepared films show preferred orientation in the [100] direction of the rutile structure of SnO2. Nonequilibrium film growth process results in doping Co into SnO2 much above the thermal equilibrium limit. A Film with 3% of Co is ferromagnetic at room temperature with a remanent magnetization of ∼26% and a coercivity of ∼9.0 mT. As Co doping content x increases, the optical band gap absorption edge (E 0) of the Co-doped SnO2 thin films initially shows a redshift at low x up to x =0.12 and then increases at the higher x, which are attributed to the sp–d exchange interactions and alloying effects, respectively. [Copyright &y& Elsevier]

We have investigated the spatially resolved local electronic properties of a nanostructured film of a colossal magnetoresistive (CMR) material by local conductance mapping (LCMAP) using a variable temperature scanning tunneling microscope (STM) operating in a magnetic field. The nanostructured thin films (thickness ap500 nm) of the CMR material La0.67Sr0.33MnO3 (LSMO) on silicon substrates were prepared using chemical solution deposition (CSD) process. These films have a large density of natural incoherent grain boundaries (GBs) which leads to significantly different behavior compared to oriented and epitaxial films of the same composition. Due to the presence of the GBs, these films show substantial low field magnetoresistance (LFMR) followed by a slower and almost linear decrease at higher fields and this is found to be strictly dependent on particle size. Most of the mechanisms proposed to explain the LFMR in the GB are based on tunneling through the GB. The purpose of this study is to use different STM based techniques to image these inhomogeneities and quantify them to the extent possible. In particular, we study the effect of grain size and the grain boundaries and their role in the electrical transport in nanostructured films of CMR materials [ABSTRACT FROM PUBLISHER]

Abstract: A new generation of CMOS-compatible micro-inductor prototypes with magnetic cores were realized, characterised as well as theoretically modelled in a frequency range up to 4GHz, a frequency range where, e.g., mobile communication and global positioning systems (GPS) are operated. The micro-inductor''s electrical magnitudes like inductance (L) and quality factor (Q) were theoretically described by means of an equivalent circuit model taking the frequency behaviour of the magnetic film core, expressed by the Landau-Lifschitz and Maxwell equations, into account. Six inch targets were used to deposit metallic layers (Al99Si0.5Cu0.5), diffusion barriers (Si3N4), insulating layers (SiO2) and magnetic films (Fe39Co30Ta8N23) by DC or reactive r.-f.-magnetron sputtering. All film materials were patterned by NUV-lithography (Near Ultra Violet), plasma beam milling and reactive ion etching to form the micro-inductors on 4-inch silicon wafers. The inductor windings are arranged in a way that they possess a low resistance and generate a quasi closed flux at the end of the cores to minimise eddy current losses in the silicon substrate. In order to diminish demagnetising effects in an efficient working core the magnetic films were patterned into micro squares with lateral dimensions of 20 and 100μm with 100nm in thickness. More magnetic volume and a higher micro-inductor cross-section was achieved by producing 100nm magnetic double layers separated by a 800nm thick Si3N4 inter-layer. To guarantee a sufficiently high cut-off frequency of the magnetic films, they were annealed in a static magnetic field at a temperature of 400°C for uniaxial anisotropy induction. This represents a temperature treatment where aluminium CMOS processes take place. As a result of patterning, the magnetic film material exhibited a remarkable increase of the cut-off frequency from 2GHz in laterally extended films up to 3.2GHz which could be also observed in the measured frequency dependent inductance and quality factor. This was accompanied by an acceptable decrease of the initial permeability that still enabled initial inductances between 1 and 2nH to be attained. [Copyright &y& Elsevier]

Abstract: The magnetization reversal of the magnetically soft permalloy layer in a spin-valve-like FeNi/Cu/Co trilayer was studied using photoelectron emission microscopy combined with X-ray magnetic circular dichroism, which allows to image the magnetic domain structure in an element-selective way. Nanosecond-short magnetic field pulses with amplitudes between 3.3 and 16.3mT were applied one by one to reverse the magnetization of the FeNi layer. Images of the magnetic domain structure were taken after application of each pulse, and the mobility of magnetic domain wall motion in the FeNi layer was deduced. The reversal mechanism of the FeNi layer was found to depend on the applied pulse length, amplitude, and on the energy and direction of the coupling between the two ferromagnetic layers. [Copyright &y& Elsevier]

High-resolution optical techniques for imaging magnetic domains in ferromagnetic materials such as confocal microscopy and scanning near-field optical microscopy (SNOM) are reviewed. The imaging capabilities of different techniques and image formation are discussed in the case of in-plane as well as out-of-plane magnetic anisotropy in different illumination configurations. It is shown that the magnetooptical resolution of near-field measurements depends on the film thickness and is limited by the diffraction on magnetic domains throughout the film. For thin magnetic films, subwavelength resolution can be attained. In addition to well-known near-field magnetooptical effects (out-of plane magnetization sensitivity of linear near-field microscopy and in-plane magnetization sensitivity of nonlinear near-field measurements), linear SNOM imaging of in-plane magnetization in thin magnetic films as well as nonlinear imaging of out-of-plane domains has been demonstrated. Thus, linear and second-harmonic near-field imaging of both in-plane and out-of-plane oriented magnetic domains can be achieved in transparent and opaque specimens. This enables applications of SNOM for studies of all kinds of magnetic materials. High-resolution optical imaging is required for characterization of the micro-magnetic and magnetooptical properties of novel magnetic structures in order to adopt a bottom-up approach in the search for new materials with improved characteristics. [ABSTRACT FROM PUBLISHER]

Magnetisation switching process and corresponding domain structures of mesoscopic ferromagnetic junction with different thickness are studied with micromagnetic simulation using Landau–Lifshiz–Gilbert equations. It is demonstrated by simulation results that the reversal process and switching field are dominated by the wide pad parts and only weakly depend on the wire parts. [Copyright &y& Elsevier]

Compositional and temperature dependencies of saturation magnetization (Ms) and uniaxial magnetocrystalline anisotropy (Ku) are determined using single crystal CoCr-alloy thin films. Temperature dependencies of Ms and Ku are stronger with increasing Cr content. Ms(OK) and Curie temperature (Tc) decrease linearly with increasing Cr content in a Co-Cr-X (X=Ta, Pt) system. Ms(OK) and Tc become zero at the Cr concentration of 33 at.%, Co-Cr-Pt specimens have higher Tc and higher Ku than those of Co-Cr-Ta specimens with similar Cr concentration. The magnetic properties of polycrystalline medium are confirmed to depend strongly on those of Co-rich core crystalline grains in Cr segregated microstructure. [ABSTRACT FROM PUBLISHER]

Recent works on perpendicular recording media were reviewed, Co-Cr alloy films are still under improvment and show a recording ability of 20 Gbit/in2 and beyond. New perpendicular recording media that have high perpendicular anisotropy have been developed. These would be candidate media for ultrahigh density recording beyond 100 Gbit/in2. [ABSTRACT FROM PUBLISHER]

The high pressure d.c. sputtering method has been used to fabricate (YBa/sub 2/Cu/sub 3/O/sub 7//Nd/sub 0.67/Sr/sub 0.33/MnO/sub 3-y/)//sub n/ [(YBCO/NSMO)/sub n/] superlattices. X-ray analyses show c-axis epitaxial growth on LaAlO/sub 3/ (100) substrates. Nd/sub 0.67/Sr/sub 0.33/MnO/sub 3-y/ films are strained due to some difference in lattice parameters between substrate and YBCO sublayers. Magnetization measurements done on single NSMO films show ferromagnetic order below 200 K. Magnetic moment measured for the superlattices below superconducting transition show ferromagnetic order and superconductivity. Such a behavior indicates on the co-existence of superconductivity and ferromagnetism in the total volume of heterostructures, where superconductivity is related to the YBCO sublayer and ferromagnetism to the NSMO sublayer. [ABSTRACT FROM PUBLISHER]

The mixed-valence manganites (A/sub 0.7/B/sub 0.3/)MnO/sub 3/ are prospective barrier materials for high-T/sub c/ junctions. They exhibit colossal magnetoresistance (CMR) and are chemically and structurally compatible with YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO). The resistivity can be varied by an impressive 11 orders of magnitude upon substitution of the cations A and B. We have studied the magnetisation and resistivity of La/sub 0.7/Ca/sub 0.3/MnO/sub 3/ (LCMO) thin films in grown epitaxially with YBCO by pulsed-laser deposition. We report here on the fabrication of c-axis oriented YBCO trilayer junctions employing LCMO as a barrier material. The crystal structure and surface morphology of a series of heterostructures has been studied using XRD and atomic force microscopy. The current-voltage characteristics have been measured as a function of temperature and magnetic field. In contrast to previously reported results the resulting devices exhibit no supercurrents. We propose the Glazman-Matveev inelastic tunnelling via localised states as a possible conduction mechanism for quasiparticle transport through the manganite barrier. [ABSTRACT FROM PUBLISHER]

Two different lithographic techniques have been developed for fabricating magnetic nano-elements on ultra-thin electron-transparent substrates thereby allowing transmission electron microscopy to be used to investigate their properties. Here we describe studies of elements of micropolycrystalline Permalloy and cobalt whose thicknesses lie in the range 20-30 nm. Bright field images show that a high degree of edge acuity is attained and elements with lateral dimensions /spl ap/25 nm have been produced. Lorentz microscopy has provided unique insight into the detailed magnetisation reversal mechanisms in acicular elements with widths in the range 100-300 nm. In cobalt elements a single domain occupies most of the volume with complex domain structures existing very close to the ends; switching fields increase markedly with decreasing element width but are substantially independent of element length. The reversal mechanism is found to involve the propagation of a small "reversing" domain structure along the element length. In Permalloy, extensive domain structures are observed in all but the narrowest elements in the remanent state. The response to applied fields is described. [ABSTRACT FROM PUBLISHER]

Properties of nanolayers can substantially differ from those of bulky materials, in part due to pronounced interface effects. It is known that combinations of layers of heavy and ferromagnetic metals leads to the appearance of specific spin textures induced by interface-induced Dzyaloshinskyi–Moria interaction (DMI), which attracts much interest and requires further studies. In this paper, we study magneto-optical effects in two- and three-layer films composed of a few nanometer thick Co layer adjacent to nanofilms of non-magnetic materials (Pt, W, Cu, Ta, MgO). For experimental studies of the interface magnetization-induced effects, we used the optical second harmonic generation (SHG) technique known for its high sensitivity to the symmetry breaking. We found that the structural asymmetry leads to the increase of the averaged SHG intensity, as well as to the magnetic field-induced effects in SHG. Moreover, by choosing the proper geometry of the experiment, we excluded the most studied linear in magnetization SHG contributions and, thus, succeeded in studying higher order in magnetization and non-local magnetic effects. We revealed odd in magnetization SHG effects consistent with the phenomenological description involving inhomogeneous (gradient) magnetization distribution at interfaces and found them quite pronounced, so that they should be necessarily taken into account when analyzing the non-linear magneto-optical response of nanostructures. [ABSTRACT FROM AUTHOR]

Although the effects of high frequency electromagnetic wave on magnetization reversal are extensively studied, the influence of low frequency ac field on magnetization reversal is seldom studied. In this research, the magnetoresistance measurement is performed to study the switching field variation under ac fields of frequencies 25 kHz, 405 kHz, and 750 kHz applied in different directions with respect to ferromagnetic elliptical thin films. It can be observed that the switching fields of the ellipses subject to in-plane ac fields are reduced significantly compared to the case without ac field, the reduction of the switching field can be up to 17% in this experiment. However, the switching fields of the ellipses subject to out-of-plane ac fields are not reduced compared to the case without ac field. [ABSTRACT FROM AUTHOR]

We present the results of a systematic change of magnetic-domain structure of epitaxial Mans film on GaAs(001) in a temperature range of 17.5 °C-45 °C by magnetic-force microscopy (FM). As temperature decreases, the small localized domains are formed and gradually collapse to the stripe domains. Finally, at 17.5 ° C the whole film turns to be a nearly single magnetic domain including only a small fraction of the non ferromagnetic β-Mans phase, as directly confirmed in the FM experiment. [ABSTRACT FROM AUTHOR]

A previous polarized neutron reflectivity study of IrMn-based spin valves demonstrated that domain wall formation during training is influenced by the thickness of the ferromagnetic pinned layer. However, magnetoresistance measurements and x-ray reflectivity of spin valves with the same nominal structure revealed that sample roughness may also affect the characteristics of the exchange bias, and thus the type of domain walls that develop. To probe the interplay between structural roughness and domain formation, we measured diffuse neutron scattering from a sample with a thick pinned layer (15 nm) and extracted the field evolution of the in-plane correlation length. At saturation, the correlation length was estimated to be 750 ±50 nm and originates from magnetic roughness. The correlation length at intermediate fields decreases to 340 nm or less and signifies the formation of in-plane domains. These results suggest that structural roughness enhances the formation of perpendicular domain walls during training. [ABSTRACT FROM AUTHOR]

The spin–spin interactions between chiral molecules and ferromagnetic metals were found to be strongly affected by the chiral induced spin selectivity effect. Previous works unraveled two complementary phenomena: magnetization reorientation of ferromagnetic thin film upon adsorption of chiral molecules and different interaction rate of opposite enantiomers with a magnetic substrate. These phenomena were all observed when the easy axis of the ferromagnet was out of plane. In this work, the effects of the ferromagnetic easy axis direction, on both the chiral molecular monolayer tilt angle and the magnetization reorientation of the magnetic substrate, are studied using magnetic force microscopy. We have also studied the effect of an applied external magnetic field during the adsorption process. Our results show a clear correlation between the ferromagnetic layer easy axis direction and the tilt angle of the bonded molecules. This tilt angle was found to be larger for an in plane easy axis as compared to an out of plane easy axis. Adsorption under external magnetic field shows that magnetization reorientation occurs also after the adsorption event. These findings show that the interaction between chiral molecules and ferromagnetic layers stabilizes the magnetic reorientation, even after the adsorption, and strongly depends on the anisotropy of the magnetic substrate. This unique behavior is important for developing enantiomer separation techniques using magnetic substrates. [ABSTRACT FROM AUTHOR]

We have observed the magnetic domain evolution under an external magnetic field in an epitaxial MnAs film on GaAs(001) by magnetic force microscopy. Owing to the strain involved, the ferromagnetic α-MnAs and the paramagnetic β-MnAs phases coexist as self-aligned stripes at room temperature. It was found that a complex magnetic domain structure appeared in the ferromagnetic α-phase region at the demagnetized state (H = 0 Oe). As the magnetic field increased, the magnetic domain structure was gradually changed, and reached a completely saturated state at H = 600 Oe. Especially, at H 300 Oe, the observed magnetic domain wall distribution is well matched with the topographical shape. [ABSTRACT FROM AUTHOR]

We have applied a developed HTS dc SQUID based magnetic microscope for study of the magnetic properties of ultrathin Ni films. A magnetic moment sensitivity close to 10/sup -15/ A.m/sup 2//Hz/sup 1/2/ has been obtained at 77 K. The space resolution was determined at level of 100 /spl mu/m by the separation between the SQUID and the studied film surface. One-domain structure, in-plane orientation of magnetic moment and ferromagnetic-like ordering in 26 /spl Aring/ thick film were found. An absolute value of the film magnetic moment has been estimated. [ABSTRACT FROM PUBLISHER]

We describe the construction of a thermomagnetic analyser that uses a microfurnace. The equipment can work in the temperature range of -30/spl deg/C up to 1000/spl deg/C, with heating/cooling rates as high as 50/spl deg/C/min. without temperature hysteresis. The design allows the use of excitation and pick-up coils with thousands of turns, working at room temperature. This gives a high sensitivity to the equipment as revealed by the measurement of magnetic transitions in thin films with masses in the order of 500 /spl mu/g. The reproducibility of the measurements is very good, and there is only noticeable drift in the most sensitive range. [ABSTRACT FROM PUBLISHER]

The permeability of amorphous non-magnetostrictive flexible ferromagnetic films is investigated in the 10 MHz to 1.6 GHz range. The permeability of melt-spun ribbons is shown to increase after chemical thinning, but no improvement is seen concerning losses in this frequency range. It is shown that demagnetizing fields affect the measured permeability, either because of finite sample size effects, or because of thickness inhomogeneities. Thinner layers were manufactured by ion beam sputtering using the melt spun ribbons as targets. Real permeability levels of 500 and resonance frequencies close to 1 GHz are observed on the layers sputtered on Kapton as well as on that sputtered on glass substrates. After annealing, flexible material with initial permeability higher than 1500 and resonance frequency of 530 MHz is produced. The study of the permeability on a broad frequency range indicates that the occurrence of high frequency losses in the hundred MHz range is-due not to skin effect but to intrinsic damping of the gyromagnetic resonance. [ABSTRACT FROM PUBLISHER]

Magnetic anisotropy energy and magnetization reversal mechanism were investigated in the glass/Tb-Fe-Co(MO)/Al films with the MO layer thickness t/sub MO/ 3 to 10 nm. As t/sub MO/ decreases, an easy magnetization direction changed from perpendicular to parallel to a film plane at t/sub MO/ of about 4 nm. Measurements of rotational hysteresis loss suggested that the magnetization reversal in the films seems to be an incoherent curling mode. [ABSTRACT FROM PUBLISHER]

The manner in which magnetization reversal process of coupled NiFeCo films are affected by various surface topography conditions of integrated circuit (IC) underlayers was examined. The experimental results demonstrated that the topography of underlayers play a significant role in affecting the magnetization reversal characteristics of the coupled films. A hysteresis loop with lower coercivity and homogeneous switching field distribution can be obtained for the coupled films deposited on underlayer with a smooth surface topography. When the coupled films were deposited on underlayers having severe surface topography, a hysteresis loop with higher coercivity and inhomogeneous switching field distribution was obtained. Such behavior may be attributed to induced inhomogeneous coupling in the coupled films due to the severe topography. [ABSTRACT FROM PUBLISHER]

Ni/sub 79/Fe/sub 21/ single layers and multilayers composed of Ni/sub 79/Fe/sub 21/ layers and paramagnetic Al interlayers were deposited using the facing targets sputtering (FTS) apparatus. During layer deposition, the external field H/sub ex/ of 200 Oe along the film plane was applied parallel or transverse to the direction of the plasma confining field H/sub p/ of about 30 Oe in the FTS apparatus. The application of H/sub ex/ parallel to the H/sub p/ direction was not significantly effective for improving soft magnetic characteristics of the films. When H/sub ex/ was applied transverse to the H/sub p/ direction, the relative permeability /spl mu//sub r/ of the Ni-Fe single layers 100 nm-thick was increased, while the coercivity H/sub c/ and the squareness ratio M/sub r//M/sub s/ of them were not varied. On the other hand, /spl mu//sub r/ of the [Ni-Fe/Al]/sub 5/ multilayers was extremely and isotropically increased while M/sub r//M/sub s/ for the multilayers was decreased down to a half value. [ABSTRACT FROM PUBLISHER]

The magnetism of sesquilayer bcc iron films on W(110) is investigated. Coercivity data and theoretical calculations indicate that the freezing of the magnetization at low temperatures reflects exchange-dominated domain-wall pinning rather than superparamagnetic spin-glass behaviour. [ABSTRACT FROM PUBLISHER]

The anisotropy-flow concept is applied to analyze in detail the reorientation transitions, driven by either thickness or temperature variations. The analysis brings to the fore the common underlying features in both cases. Three generic scenarios for the occurrence of the reorientation are predicted and described in both cases on general thermodynamic grounds. The method is especially effective when underpinned by the usual assumption about the explicit thickness dependence of the first two anisotropy constants. [ABSTRACT FROM PUBLISHER]

Magnetic properties of ultra-thin Fe [ABSTRACT FROM PUBLISHER]

Co-Fe-Si-B films have been prepared using a roll coater and DC magnetron sputtering system onto a polyethylene terephthalate substrate. This thin film exhibited an excellent uniaxial anisotropy introduced by an asymmetric thermal shrinkage of the substrate. Reversal with a single large Barkhausen pulse has been observed in thin film structure 1 mm by 50 mm by 0.65 /spl mu/m. Closure domains have been clearly identified at the film ends. The threshold for the reversal is the coercive force. The reason for reversal with a single Barkhausen jump is that the long narrow film geometry has essentially zero demagnetizing field over most of the film. Once the walls start to move through the center portion of the film, there is nothing to stop them so the reversal proceeds with a single large Barkhausen pulse. [ABSTRACT FROM PUBLISHER]

Ultrafine Gd particles in a Cu metallic matrix have been obtained by post-annealing of as-sputtered metastable Gd/sub x/Cu/sub 1-x/ alloys at temperatures higher than 250/spl deg/C. The results of resistivity measurements show that the resistivities of as-sputtered metastable Gd/sub 0.2/Cu/sub 0.8/ and Gd/sub 0.3/Cu/sub 0.7/ alloys exhibit a resistivity minimum at low temperatures, an indication of the Kondo effect. In addition the temperature of the resistivity minimum rises with the increasing Gd content. Conversely, the resistivity of films after formation of Gd granules levels off at low temperatures. The magnetic results indicate that the metastable GdCu alloys are essentially a spin-glass at low temperature with the transition temperatures at around 3.5/spl sim/5 K. However, magnetization data at 80 K shows that the as-sputtered samples contain some small Gd ferromagnetic clusters in the paramagnetic matrix. The magnetic particles of granular films begin to be thermally blocked at T/sub B/ and become magnetically ordered below T/sub B/. Due to larger grain sizes, T/sub B/ is much higher for x=0.3 than for 0.2. The variation of transport and magnetic properties for samples with different annealing processes are described in detail. [ABSTRACT FROM PUBLISHER]

We have studied the structure and soft magnetic properties of Fe-ceramic (Si/sub 3/N/sub 4/, Al/sub 2/O/sub 3/) thin films fabricated by an rf magnetron sputtering apparatus using a composite target. The concentration of solute in the film increases linearly with the area fraction of ceramic pieces in the target. In the case of Si/sub 3/N/sub 4/, the concentration of O increases largely with the Ar pressure, especially at high Ar pressures of more than 20 mTorr. In Al/sub 2/O/sub 3/, the composition of Al and O exhibits a maximum at the Ar pressure of 20 mTorr. As the area fraction of the ceramic increases, the structure of the film changes from a crystalline phase to an amorphous phase. The electrical resistivity increases significantly with increasing area fraction of the ceramics. The saturation magnetization decreases inversely with the logarithm of the electrical resistivity. The gradient of the decrease in saturation magnetization against electrical resistivity is lower in the Al/sub 2/O/sub 3/ system than that in the Si/sub 3/N/sub 4/ system. The Ar pressure dependences of the electrical resistivity and the saturation magnetization are similar to that of the thin film composition. Fe-Si/sub 3/N/sub 4/ films exhibited a saturation magnetization of about 8 kG, a hard-axis coercivity of 0.2 Oe, an electrical resistivity of about 800 /spl mu/ /spl Omega/-cm and a permeability (100 MHz) of higher than 400. [ABSTRACT FROM PUBLISHER]

The magnetic properties and structures of Ni and NiFe nanocrystalline films prepared with the gas-deposition method (GDM) are investigated. From the results of STM and SEM, fine particles, approximately 10 nm in diameter, were seen in the films. Furthermore, aggregates several tens of nm in diameter, composed of the small particles, are also observed. The magnetization of the Ni nanocrystalline films is about 50 emu/g, or 90% of that of bulk Ni. Coercivity of the Ni nanocrystals ranged from 4 to 20 Oe. In the case of NiFe, the concentration of Fe is slightly increased as the evaporation temperature is increased. [ABSTRACT FROM PUBLISHER]

Thin films consisting of granular dispersions of cobalt nano-particles in a hydrocarbon matrix are fabricated by simultaneous sputtering of cobalt and plasma induced polymerization of hydrocarbon monomers. It is confirmed that cobalt nano-particles with a hexagonal close-packed (hcp) structure are uniformly distributed throughout the amorphous hydrocarbon matrix. In-plane magnetic hysteresis loops obtained by MOKE (Magneto-Optic Kerr Effect) magnetometry measurements show significant differences between granular cobalt crystallites dispersed throughout the polymeric film matrix and cobalt crystallites in a continuous polycrystalline pure cobalt film due to the mechanism of domain boundary pinning. For the first time, the domain structures and wall motion in a cobalt/polymer system are captured in real time by Lorentz microscopy. [ABSTRACT FROM PUBLISHER]