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Introduction and purpose Patient risk in non-ST-segment elevation myocardial infarction (NSTEMI) depends on clinical setting, individual patient variables and procedural characteristics. Standardized risk-adjusted periprocedural management for catheterization procedures using a Standard Operating Procedure (SOP) was investigated to evaluate associations with in-hospital clinical outcomes. Methods In 01/2018, our heart center established an SOP for coronary catheterization procedures in NSTEMI, targeting 1) standardized pre-procedural risk assessment using National Cardiovascular Data Registry (NCDR) risk models, and 2) standardized post-procedural risk-adjusted safety measures, including advanced patient monitoring (intermediate/intensive care) and use of vascular closure devices. All patients presenting with invasively-managed NSTEMI in 2018 were retrospectively evaluated for SOP-based pre-procedural risk scoring, SOP-based post-procedural management and in-hospital clinical outcomes of mortality, major bleeding (MB, according to BARC ≥3) and acute kidney injury (AKI, according to KDIGO). Results A total of 430 patients (age 72±12 years, 71% male, BMI 27±5) presenting with NSTEMI from 01 to 12/2018 were included, 9.8% presented in cardiogenic shock and 4.7% had suffered a preclinical cardiac arrest. Overall in-hospital mortality was 3.7%, MB occurred in 6.5%. 207 patients (48.1%, SOP+ group) had received both 1) pre-procedural risk assessment and 2) post-procedural risk-adjusted safety measures; the other 223 patients (51.9%, SOP- group) had not received either 1) or 2). There were no significant differences in baseline characteristics and prior-existing medical conditions between groups, however, significantly more patients in SOP- group were treated in emergency settings (39.9% vs. 21.7%, p=0.004). However, significantly more patients in SOP- were treated in emergency settings at higher risk (39.9% (SOP-) vs. 21.7% (SOP+); p Conclusion Standardized risk management in invasively managed NSTEMI was associated with significantly lower rates of in-hospital major bleedings. Funding Acknowledgement Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): Junior Clinician Scientist Track, Medical faculty, Heinrich-Heine-University Düsseldorf, Germany

Geometrically confined magnetic particles due to their unique response to external magnetic fields find a variety of applications, including magnetic guidance, heat and drug delivery, magneto-mechanical actuation, and contrast enhancement. Highly sensitive detection and imaging techniques based on the nonlinear properties of nanomagnets were recently proposed as innovative strong-translational potential methods applicable in complex, often opaque, biological systems. Here we report on the significant enhancement of the detection capability using optical-lithography-defined, ferromagnetic iron–nickel alloy disk-shaped particles. We show that an irreversible transition between strongly non-collinear (vortex) and single domain states, driven by an alternating magnetic field, translates into a nonlinear magnetic response that enables ultrasensitive detection of these particles. The record sensitivity of ∼3.5 × 10−9 emu, which is equivalent to ∼39 pg of magnetic material is demonstrated at room temperature for arrays of patterned disks. We also show that unbound disks suspended in the aqueous buffer can be successfully detected and quantified in real-time when administered into a live animal allowing for tracing of their biodistribution. The use of nanoscale ferromagnetic particles with engineered nonlinear properties opens prospects for further enhancing the sensitivity, scalability, and tunability of noise-free magnetic tag detection in high-background environments for various applications spanning from biosensing and medical imaging to anti-counterfeiting technologies.

FePt-Fe3O4 core-shell nanoparticles functionalized with 3,4-dihydroxyphenylacetic acid (DOPAC) and dimercaptosuccinic acid (DMSA) ligands were synthesized and characterized. We found that the DOPAC ligand enhances the magnetic properties of the FePt-Fe3O4 particles, in comparison with the DMSA ligand, which induces the oxidation of the shell layer that causes a significant reduction of the saturation magnetization. The synthesized magnetic nanoparticles were evaluated for applications in magnetic hyperthermia and magnetic resonance imaging contrast enhancement.

We systematically studied the size-dependent quantum diffusion of Gd atoms within Fe circular quantum corrals on Ag(111). By varying the size of the quantum corrals, different types of patterns are observed inside the corrals, including a single dot and circular orbits for the diffusion of Gd adatoms. In addition, the motion of the adatoms also forms circular-like orbits outside the corral. Via quantitative analysis, we confirm that the regions with adatoms' high visiting probability are consistent with the positions of the local electronic density-of-states maxima, both inside and outside the corrals within a

A patterned mesoscale ferromagnetic disk in equilibrium can attain a flux closure vortex state with circumferential in-plane magnetization and an out-of-plane magnetic component (vortex core) at the center. When driven by a small-amplitude oscillating magnetic field or current, the vortex core gyrates around its equilibrium position experiencing resonance at a characteristic eigenfrequency. Here, we propose a resonant-spin-ordering approach for manipulating the relative vortex core polarities in coupled double-dot structures. This is achieved by driving the system to a chaotic regime of continuous core reversals and subsequently relaxing the cores to steady state motion. Any particular core polarity combination (and therefore the spectral response of the entire system) can be deterministically pre-selected by simply tuning the excitation frequency.

The element- and site-specificity of X-ray resonant magnetic scattering (XRMS) makes it an ideal tool for furthering our understanding of complex magnetic systems. In the hard X-rays, XRMS is readily applied to most antiferromagnets where the relatively weak resonant magnetic scattering (10 -2-10 -6I c) is separated in reciprocal space from the stronger, Bragg charge scattered intensity, I c. In ferro(ferri)magnetic materials, however, such separation does not occur and measurements of resonant magnetic scattering in the presence of strong charge scattering are quite challenging. We discuss the use of charge-magnetic interference resonant scattering for studies of ferromagnetic (FM) crystals and layered films. We review the challenges and opportunities afforded by this approach, particularly when using circularly polarized X-rays. We illustrate current capabilities at the Advanced Photon Source with studies aimed at probing site-specific magnetism in ferromagnetic crystals, and interfacial magnetism in films. © 2012 EDP Sciences, Springer-Verlag.

In our study, hybrid gold/iron oxide loaded thermoresponsive micelles were synthesized for combined hyperthermia and chemotherapy, and optical imaging. Polymeric micelles made of amphiphilic block copolymer of poly(N-isopropylacrylamide-co-acrylamide)-block-poly(epsiv-caprolactone) were conjugated with gold/iron oxide particles which are self-assembled at the hydrophobic polymer core. Thermal sensitivity and magnetic and optical properties of the hybrid gold/iron oxide micelles were investigated for the combined therapy and optical imaging.

We demonstrate a magneto-optic technique to measure Brownian relaxation of magnetic nanoparticles suspended in liquids. We used AC susceptibility data as a function of frequency of the applied AC magnetic field to verify that the results agree with those obtained via a conventional inductive detection technique. However, compared with a commercial AC susceptometer using the conventional detection scheme, our magneto-optic setup is able to detect a density of nanoparticles at least three orders smaller. This technique has the potential of being used as a sensor for magnetic nanoparticles such as in local temperature, viscoelasticity, or molecular-binding measurements.

Injection and detection of non-local spin accumulation have been demonstrated in a series of nanoscale metallic lateral spin valves, fabricated by electron beam lithography. A distinct feature of non-local spin valves is that a pure spin current without charge flow can be generated. The measured spin signal is only sensitive to the relative orientations of the detector spin and the spin accumulation, and exhibits little charge background voltage. The injection polarizations of the interfaces and the spin diffusion lengths of the non-magnetic components have been determined by measuring the spin signals from a set of similar spin valves with varying injector and detector separations. In Py/Au/Py lateral spin valves, where Py is permalloy, the injection polarization across the Py/Au interface is 3%, and the spin diffusion length of Au is 63 ± 15 nm at 10 K. In Co/Cu/Co lateral spin valves, the injection polarization across the Co/Cu interface is increased to over 7%, due to better interfacial quality compared with Py/Au. The spin diffusion length of Cu is 200 ± 20 nm at 10 K, and > 110 nm at 300 K.

An overview is provided of recent work at Argonne that covers three aspects of nanomagnetism. The first is in the area of spin transport, where all-metallic lateral spin valves are explored. The second is in the area of spin dynamics, where a variety of magnetic vortex geometries are summarized. And the third is in the area of self-assembly, where capsid templates derived from viruses are used to contain the growth of magnetic nanoparticles. In each case issues are highlighted associated with the relation between magnetism and structure.

We review the correlation of magnetism and surface structure in ultrathin metal films, including the tailoring of novel magnetic properties using atomic scale control of the nanostructure. We provide an overview of modern fabrication and characterization techniques used to create and explore these fascinating materials, and highlight important phenomena of interest. We also discuss techniques that control and characterize both the magnetic and structural properties on an atomic scale. Recent advances in the development and applications of these techniques allow nanomagnetism to be investigated in an unprecedented manner. A system cannot necessarily retain a two-dimensional structure as it enters the ultrathin region, but it can transform into a three-dimensional, discontinuous structure due to the Volmer–Weber growth mechanism. This structural transformation can give rise to superparamagnetism. During this evolution, competing factors such as interparticle interactions and the effective magnetic anisotropy govern the magnetic state. These magnetic parameters are influenced by the nanostructure of the film. In particular, controlling the magnetic anisotropy is critical for determining the magnetic properties. Surface effects play especially important roles in influencing both the magnitude and direction of the magnetic anisotropy in ultrathin films. By properly altering the surface structure, the strength and direction of the magnetic anisotropy are controlled via spin–orbit and/or dipole interactions.

The field of spintronics, or magnetic electronics, is maturing and giving rise to new subfields. These new directions involve the study of collective spin excitations and couplings of the spin system to additional degrees of freedom of a material, as well as metastable phenomena due to perturbations that drive the system far from equilibrium. The interactions lead to possibilities for future applications within the realm of energy-efficient information technologies. Examples discussed herein include research opportunities associated with (i) various spin-orbit couplings, such as spin Hall effects, (ii) couplings to the thermal bath of a system, such as in spin Seebeck effects, (iii) spin-spin couplings, such as via induced and interacting magnon excitations, and (iv) spin-photon couplings, such as in ultra-fast magnetization switching due to coherent photon pulses. These four basic frontier areas of research are giving rise to new applied disciplines known as spin-orbitronics, spin-caloritronics, magnonics, and spin-photonics, respectively. These topics are highlighted in order to stimulate interest in the new directions that spintronics research is taking, and to identify open issues to pursue.

Low dimensional nanostructures have attracted attention due to their rich physical properties and potential applications. The essential factor for their functionality is their electronic properties, which can be modified by quantum confinement. Here the electronic states of Gd atom trapped in open Fe corrals on Ag(111) were studied via scanning tunneling spectroscopy. A single spectroscopic peak above the Fermi level is observed after Gd adatoms are trapped inside Fe corrals, while two peaks appear in empty corrals. The single peak position is close to the higher energy peak of the empty corrals. These findings, attributed to quantum confinement of the corrals and Gd structures trapped inside, are supported by tight-binding calculations. This demonstrates and provides insights into atom trapping in open corrals of various diameters, giving an alternative approach to modify the properties of nano-objects.

The recent development of bio-conjugated magnetic nanoparticles offers many opportunities for applications in the field of biomedicine. In particular, the use of magnetic nanoparticles for biosensing has generated widespread research efforts following the progress of various magnetic field sensors. Here we demonstrate substrate-free biosensing approaches based on the Brownian rotation of ferromagnetic nanoparticles suspended in liquids. The signal transduction is through the measurement of the magnetic ac susceptibility as a function of frequency, whose peak position changes due to the modification of the hydrodynamic radius of bio-conjugated magnetic nanoparticles upon binding to target bio-molecules. The advantage of this approach includes its relative simplicity and integrity compared to methods that use substrate-based stray-field detectors.

The search for high-density recording materials has been one of most active and vigorous field in the field of magnetism. FePt-L1? nanoparticle has emerged as a potential candidate because of its high anisotropy. In this paper, we provide an overview of recent work at Argonne National Laboratory that contributes to the ongoing dialogue concerning the relation between structure and properties of the FePt nanoparticle system. In particular we discuss the ability to control structure and properties via dosing with Cr. Cr-dosed FePt films were grown via molecular beam epitaxy and annealed at 550℃ in an ultrahigh vacuum chamber, and were studied with the surface magneto-optic Kerr effect (SMOKE), scanning electron microscopy (SEM) and x-ray magnetic circular dichroism (XMCD). We found that small dosage of Cr helps to generate L1? phase FePt magnetic nanoparticles with small size, defined shape and regular spatial distribution on MgO (001) substrate. The nanostructures are ferromagnetic with high magnetic coercivity (~0.9T) and magnetic easy axis in the desired out-of-plane orientation. We also show that controlling the lateral region where nanostructures exist is possible via artificial patterning with Cr.

This report examines the current status and the future directions of the field of nanomagnetism and assesses the ability of hard X-ray synchrotron facilities to provide new capabilities for making advances in this field. The report first identifies major research challenges that lie ahead in three broadly defined subfields of nanomagnetism: confined systems, clusters and complex oxides. It then examines the relevant experimental capabilities that are currently available at hard X-ray synchrotron light sources, using the Advanced Photon Source (APS) at Argonne as an example. Finally, recommendations are made for future development in X-ray facilities that will enhance the study of nanomagnetism, including new experimental directions, modifications that would enable in situ sample preparation, and measurements at high magnetic fields and/or low temperatures. In particular, in situ sample preparation is of high priority in many experiments, especially those in the area of surface magnetism.

The growth of cobalt, iron, and platinum and their alloy nanoparticles was investigated with oleic acid and trioctylphosphine oxide as ligands. Both the ligand type and concentration are important in determining the final product of the reactions. With a high concentration of oleic acid, thermal decomposition of dicobalt octacarbonyl and iron pentacarbonyl precursors yields only molecular cluster complex species with oxidized metal centers. However, reduction of platinum acetylacetonate under identical conditions yields nanometer-sized particles. In the presence of a high concentration of trioctylphosphine oxide, only the cobalt system was observed to form a cluster−complex species, while both the iron and platinum systems form nanometer-sized particles. This oxidation process, which forms cluster complexes, provides a digestive ripening mechanism that competes with the Ostwald ripening process, thus affecting the particle size and composition of both the pure metal and alloy nanoparticles.

A laser beam, precisely focused on the patterned superconducting structure, was used to nucleate a resistive area that is sensitive to external thermal effects. The electron beam lithography and wet chemical etching were applied as pattern transfer processes in epitaxial Y-Ba-Cu-O films. Two different sensor designs were tested: (i) 3 millimeters long and 40 micrometers wide stripe and (ii) 1.25 millimeters long, and 50 micron wide meander -like structure. It is shown experimentally that scanning the laser beam along the stripe leads to physical displacement of the sensitive area and, therefore may be used as a basis for imaging over a broad spectral range. For example, patterning the superconducting film into a meander structure is equivalent to a two-dimensional detector array. In additional to the simplicity of the detector fabrication sequence (one step mask transfer), a clear advantage of this approach is the simplicity of the read-out process: an image is formed by registering the signal with only two electrical terminals. The proposed approach can be extended for imaging over a wide spectral range.

Nanomagnetism is the discipline dealing with magnetic phenomena specific to structures having dimensions in the submicron range. This Colloquium addresses the challenges and scientific problems in this emerging area, including its fabrication strategies, and describes experiments that explore new spin-related behaviors in metallic systems as well as theoretical efforts to understand the observed phenomena. As a subfield of nanoscience, nanomagnetism shares many of the same basic organizing principles such as geometric confinement, physical proximity, and chemical self-organization. These principles are illustrated by means of several examples drawn from the quests for ultrastrong permanent magnets, ultra-high-density magnetic recording media, and nanobiomagnetic sensing strategies. As a final example showing the synergetic relationships to other fields of science, this Colloquium discusses the manipulation of viruses to fabricate magnetic nanoparticles.

Phase-segregated block copolymers have received significant attention in the last decade as enabling materials for future technologies. Their value to nanotechnology derives from the expedient tunability of the size, shape, and periodicity of the self-assembled domains by means of manipulating molecular characteristics. Recently, the potential opportunities for block copolymer applications have been bolstered by new methods, which give fine control over long-range ordering of the microdomain structures. Thin polymer films, by themselves, have limited device applications, but myriad functions can be addressed with hybrid hard/soft matter systems in which the organic layer is used as a scaffold for nanoscale organization of inorganic materials. Of specific interest is the interaction of surfactant-mediated colloidal nanoparticles and diblock copolymer films because the nanocrystal capping molecules can be tailored to exhibit preference for one of the polymer blocks. This hierarchical approach to create ordered nanostructures removes the linear correlation of size and patterning time associated with traditional lithographic techniques by self-assembling the entire surface in parallel. Also, the spatial limits of lithography can be transcended and the approach can potentially be adapted to industrial-scale processing. An alternative approach to the colloidal nanocrystal methodology is to use spherical- or cylindrical-phase diblock copolymers as etch masks to produce self-assembled arrays of nanoscale dots, pillars, or lines composed of various materials. The advantage of our approach is that the length-scale of the final functional material is an order of magnitude smaller than the original polymer domains.

Nanostructured magnetic materials are intensively studied due to their unusual properties and promise for possible applications. The key issues in these materials relate to the connection between their physical properties (transport, magnetism, mechanical, etc.) and their chemical-physical structure. In principle, a detailed knowledge of the chemical and physical structure allows calculation of their physical properties. Theoretical and computational methods are rapidly evolving so that magnetic properties of nanostructured materials might soon be predicted. Success in this endeavor requires detailed quantitative understanding of the magnetic structure and properties.

The elementary events of the remagnetization processes in nanocomposite magnetic bilayers were investigated using iron-garnet indicator films with in-plane anisotropy. We have observed hybrid domain walls consisting of both ferromagnetic and antiferromagnetic sections perpendicular to the interface. The external magnetic field shifts only the ferromagnetic part of the domain walls. This leads to the formation of a hybrid exchange spin spring parallel to the interface. The processes of spring nucleation and untwisting occur at different locations. With the field oriented antiparallel to the macroscopic unidirectional anisotropy, remagnetization of the soft ferromagnet layer in the hard/soft nanocomposite starts by the formation of an exchange spring consisting of micrometer-scale sub-domains with opposite direction spin twisting. A rotating magnetic field (smaller than some critical value) creates firstly a single-chiral spin spiral; this spiral then loses stability, incoherently untwists and gradually inverts its chirality with increasing field rotation. Untwisting of the hybrid exchange spring at higher fields leads to the creation of unusual hybrid non-180° domain walls. The initial (ground) state of the bilayer with such noncollinear magnetized domains is not restored after stopping the field rotation and returning it to zero. The revealed phenomena are attributed to the influence of the dispersion in the unidirectional anisotropy induced by magnetization frustration in the interface and bilayer crystal lattice defects.

X-ray emission and absorption spectroscopy (XES and XAS, respectively) are important and powerful techniques for determining the electronic properties of materials. Both are used to study magnetic circular dichroism (MCD) which is especially useful for analyzing the magnetic properties of materials. We present XAS and XES measurements and a MCD model study of two thin film layered samples containing SmCo layers in order to report on the applicability of soft x-ray spectroscopic techniques to determine the composition, layer thickness, and electronic structure of such materials. Using a transmission by fluorescence attenuation (TFA) technique we determined the composition and thickness of the SmCo layer to be consistent with the intended composition and thickness. We also confirmed the thickness of the other layers by comparing the XES from the thin film with that of a bulk sample. We showed by a model study that TFA could be used to obtain MCD, and thus the anisotropy of the sample, for film thicknesses b...

Magnetic and chemical heterogeneity are common in a broad range of magnetic thin film systems. Emerging resonant soft x-ray scattering techniques are well suited to resolve such heterogeneity at relevant length scales. Resonant x-ray magneto-optical Kerr effect measurements laterally average over heterogeneity but can provide depth resolution in different ways, as illustrated in measurements resolving reversible and irreversible changes in different layers of exchange-spring heterostructures. Resonant small-angle scattering measures in-plane heterogeneity and can resolve magnetic and chemical scattering sources in different ways, as illustrated in measurements of granular alloy recording media.

La 0.67 Ca 0.33 MnO 3 - δ thin films were deposited using a high-pressure dc-sputtering process. Pure oxygen at a pressure of 3.8 mbar was used as sputtering gas. The films were grown on (001) LaAlO 3 and (001) SrTiO 3 substrates at heater temperature of 850° without any annealing treatment. The formation of highly a-axis-oriented films with sharp interface with substrate surface is demonstrated by X-ray diffraction, transmission electron microscope (TEM), and atomic force microscope (AFM) analysis. Electrical characterization revealed a metal–insulator transition at T MI = 276 K, and magnetic characterization showed good magnetic properties with a PM–FM transition at TC ≈ 262 K.

In the study of spin dependent magnetic tunneling junctions, the switching stability of the magnetically hard layer is a crucial issue for long-term use in magnetic random access memory. After N switching cycles of the soft layer, the hard layer would be demagnetized due to the stray field from the domain wall created during switching of the soft layer. Therefore, reducing the stray field from the soft layer is the way to increase switching stability. In this study, we propose a structure which replaces the usual soft layer (typically permalloy, Fe, or Co) with an artificial ferrimagnet to reduce the stray field. The artificial ferrimagnet consists of a trilayer with an interlayer that antiferromagnetically couples two ferromagnetic layers of unequal thickness. The total stray field from the artificial ferrimagnet structure can be approximated as the sum of the stray fields from the two ferromagnetic layers. Since the sign of the stray field of the two layers is opposite, due to antiferromagnetic coupling...

Theoretical and experimental issues connected with exchange-bias and exchange-spring behaviour are briefly reviewed, and the potential of conversion electron Mossbauer spectroscopy, including the 57Fe probe layer technique, to reveal the spin structure in layered systems is emphasized. First experimental results are reported for the new exchange-bias system FeSn2/Fe and for the exchange-spring system Sm–Co/Fe.

We highlight our experimental studies and micromagnetic simulations of the rotational hysteresis in exchange-spring magnets. Magneto-optical imaging and torque magnetometry measurements for Sm–Co/Fe exchange-spring films with uniaxial in-plane anisotropy show that the magnetization rotation created in the magnetically soft Fe layer by a rotating magnetic field is hysteretic. The rotational hysteresis is due to the reversal of the chirality of the spin spiral structure. Micromagnetic simulations reveal two reversal modes of the chirality, one at low fields due to an in-plane untwisting of the spiral, and the other, at high fields, due to an out-of-plane fanning of the spiral.

The remagnetization of a soft ferromagnetic film exchange coupled with a high-coercivity ferromagnetic film is studied by a magneto-optic imaging technique. If the magnetic field is antiparallel to the macroscopic unidirectional in-plane anisotropy, the soft layer reverses via the formation of exchange springs consisting of subdomains with opposite spin twistings. However, if the field is instead rotated in-plane, remagnetization initially proceeds via formation of a single uniform exchange spring. Then, at a critical angle, the spring incoherently untwists, leading again to subdomains with opposite chirality. These phenomena are attributed to the influence of inhomogeneity in the unidirectional magnetic anisotropy.

The collective creativity of those working in the field of surface magnetism has stimulated an impressive range of advances. Once wary, theorists are now eager to enter the field. The present article attempts to take a snapshot of where the field has been, with an eye to the more speculative issue of where it is going. Selective examples are used to highlight three general areas of interest: (i) characterization techniques, (ii) materials properties, and (iii) theoretical/simulational advances. Emerging directions are identified and discussed, including laterally confined nanomagnetism and spintronics.

It is shown experimentally that in a two-dimensional array of Permalloy nanodots the lifetime of the electromagnetic microwave radiation at the sub-harmonic frequency originated from the parametrically excited ferromagnetic resonance mode is increased by two orders of magnitude compared to the case of a continuous magnetic film.

We present measurements of the spin Hall effect using macroscopic spin currents generated from spin pumping. Measurements as a function of layer thickness enable the determination of the spin diffusion length, which is an essential parameter for the proper quantification of the spin Hall conductivity and the related spin Hall angle. Furthermore we discuss the temperature dependence of these measurements and how possible proximity effects may be reflected in the data.

In magnetically coupled, planar ferromagnet-superconductor (F/S) hybrid structures, magnetic domain walls can be used to spatially confine the superconductivity. In contrast to a superconductor in a uniform applied magnetic field, the nucleation of the superconducting order parameter in F/S structures is governed by the inhomogeneous magnetic field distribution. The interplay between the superconductivity localized at the domain walls and far from the walls leads to effects such as re-entrant superconductivity and reverse domain superconductivity with the critical temperature depending upon the location. Here we use scanning tunnelling spectroscopy to directly image the nucleation of superconductivity at the domain wall in F/S structures realized with Co-Pd multilayers and Pb thin films. Our results demonstrate that such F/S structures are attractive model systems that offer the possibility to control the strength and the location of the superconducting nucleus by applying an external magnetic field, potentially useful to guide vortices for computing application., When superconductivity emerges in a thin superconductor grown on a ferromagnet, it does so in an array of interacting superconducting and normally conducting channels. Maria Iavarone and colleagues use scanning tunnelling microscopy to image how these channels form and interact.

Utilizing open Fe nanocorrals built by atom manipulation, we demonstrate self-regulated Gd atom trapping in open quantum corrals. The number of Gd atoms trapped is exactly determined by the diameter of the corral. The quantization can be understood as a self-regulating process, arising from the long-range interaction between Gd atoms and the open corral. We illustrate with arrays of open corrals that such atom trapping can suppress unwanted statistical fluctuations. Our approach opens a potential pathway for nanomaterial design and fabrication with atomic-level precision.

Recent developments in the field of spin dynamics--like the interaction of charge and heat currents with magnons, the quasi-particles of spin waves--opens the perspective for novel information processing concepts and potential applications purely based on magnons without the need of charge transport. The challenges related to the realization of advanced concepts are the spin-wave transport in two-dimensional structures and the transfer of existing demonstrators to the micro- or even nanoscale. Here we present the experimental realization of a microstructured spin-wave multiplexer as a fundamental building block of a magnon-based logic. Our concept relies on the generation of local Oersted fields to control the magnetization configuration as well as the spin-wave dispersion relation to steer the spin-wave propagation in a Y-shaped structure. Thus, the present work illustrates unique features of magnonic transport as well as their possible utilization for potential technical applications.

The development of the optimal exchange-spring permanent magnet balances exchange hardening, magnetization enhancement, and the feasibility of scalable fabrication. These requirements can be met with a rational design of the microstructural characteristics. The magnetization processes in several model exchange-spring structures with different geometries have been analyzed with both micromagnetic simulations and nucleation theory. The multilayer geometry and the soft-cylinders-in-hard-matrix geometry have the highest achievable figure of merit (BH)max, while the soft-spheres-in-hard-matrix geometry has the lowest upper limit for (BH)max. The cylindrical geometry permits the soft phase to be larger and does not require strict size control. Exchange-spring permanent magnets based on the cylindrical geometry may be amenable to scaled-up fabrication.

We have studied the effect of magnetic disorder on the magnetization reversal process in thin Co/CoO-films. The antiferromagnetic CoO layer allows a reversible tuning of the magnetic disorder by simple temperature variation, which was experimentally verified by measuring the ferromagnetic resonance linewidth as a function of temperature. The Co/CoO-films exhibit a discontinuous magnetization reversal process for temperatures above a critical temperature Tc, whereas smooth magnetization loops occur for T Tc.

We investigate the magnetic properties of 200-nm thick La 0.67 Ca 0.33 MnO 3 films, which were grown under identical conditions onto five single crystal substrates: SrTiO 3 (0 0 1), LaAlO 3 (0 0 1), MgO(0 0 1), NdGaO 3 (0 0 1) and Si(1 1 1). The films exhibit a strong substrate dependence of the magnetic properties, including the coercive field, remanent magnetization and Curie temperature T C . The T C distribution was determined for each film. The upper cut-off value for the distribution is found to be virtually identical in all samples, even though the distribution width itself varies by almost an order of magnitude. The results are attributed predominantly to the degree of sample homogeneity, and are discussed in terms of strain-induced growth mode differences.

Magnetic structures of SmCo/Fe bilayers during remagnetization and after multiple field cycling are studied magneto-optically (MO). Rotation of the remanent magnetization in the soft Fe layer away from the easy axis is found after large enough remagnetizing fields. This is indicative of the appearance of biquadratic coupling between the layers. It is explained by the fluctuation exchange mechanism due to the field induced magnetic inhomogeneity of the hard layer. Such an inhomogeneity revealed in the MO patterns also explains the degradation of the bias field in exchange springs.

The complex 3-dimensional magnetization reversal behavior of Sm–Co/Fe exchange spring films is used to test the sensitivity of different resonant soft X-ray magneto-optical Kerr effect (MOKE) measurements to changes in longitudinal and transverse moments within the soft Fe layer and to changes in these moments in depth within the Fe layer. As in the visible MOKE, changes in longitudinal and net transverse moments are resolved by measuring both Kerr rotation and intensity loops, respectively, near the Fe 2p core resonance. These X-ray MOKE signals measured using linear incident polarization are more directly interpreted in terms of longitudinal and transverse moments than are the same signals measured using elliptical polarization. Varying photon energy near the Fe L 3 line is shown to be an effective means of resolving distinctly different reversal behavior at the top and bottom of the 20 nm thick Fe layer resulting from the strong exchange coupling at the Sm–Co/Fe interface. Measured X-ray MOKE spectra and signals are in qualitative agreement with those calculated using standard magneto-optical formalisms incorporating interference between different layers and measured helicity-dependent magneto-optical constants for Fe.

The magnetic field and temperature dependence of the magnetic susceptibility is studied for the ferromagnetic layered manganites SrO(La1−xSrxMnO3)2 in the composition range x=0.32–0.40. In the paramagnetic phase, the susceptibility exhibits an anomalous maximum at an intermediate magnetic field value. The size of this field-induced susceptibility enhancement increases dramatically with x from 10% for x=0.32 to 160% for x=0.40. The temperature dependence of the effect shows a maximum at T≈1.1 TC for all x. Quantitative analysis in terms of the Landau theory of phase transitions enables us to identify a distortion of the free energy F in the paramagnetic phase that is associated with the susceptibility anomaly. This free energy distortion corresponds to a magnetic system that approaches a first order magnetic phase transition as the temperature is lowered toward TC. Such a behavior is indicative of a second, competing order parameter, which is identified as the recently observed charge density wave. In the ...

In the [Fe/Cr]AF/Crx/[Fe/Cr]F double superlattices consisting of a ferromagnetic Fe/Cr superlattice on top of an antiferromagnetic Fe/Cr superlattice, the exchange coupling between the superlattices is determined by the thicknesses (x) of the Cr spacer layer. The oscillating behavior of the exchange bias field of a series of (2 1 1)-oriented Fe/Cr double superlattices was determined by superconducting quantum interference device (SQUID) and magneto-optic Kerr effect (MOKE) measurements. For x >13 A a negative strongly oscillating character of the exchange bias was observed. At very thick x the exchange bias vanishes. The most immediate result is the fact that the exchange bias field is always negative, regardless of the sign of the coupling between the ferromagnetic and the antiferromagnetic superlattices. The detailed dependence of the exchange bias field as a function of the intersuperlattice thickness of Cr is explained in terms of the interaction between the two superlattices in collinear configuration.

Structural and magnetic properties of the two-layered Ruddlesden-Popper phase SrO(La{sub 1{minus}x}Sr{sub x}MnO{sub 3}){sub 2} with x = 0.3--0.5 are highlighted. Intrinsic properties of these naturally layered manganites include a colossal magnetoresistance, a composition-dependent magnetic anisotropy, and almost no remanence. Above the Curie temperature there is a non-vanishing extrinsic magnetization attributed to intergrowths (stacking faults in the layered structure). These lattice imperfections consist of additional or missing manganite layers, as observed in transmission electron microscopy. Their role in influencing the properties of the host material is highlighted.

Utilizing the oscillatory interlayer exchange coupling in Fe/Cr superlattices, we have constructed ''double superlattice'' structures where a ferromagnetic (F) and an antiferromagnetic (AF) Fe/Cr superlattice are coupled through a Cr spacer. The minor hysteresis loops in the magnetization are shifted from zero field, i.e., the F superlattice is exchange biased by the AF one. The double superlattices are sputter-deposited with (211) epitaxy and possess uniaxial in-plane magnetic anisotropy. The magnitude of the bias field is satisfactorily described by the classic formula for collinear spin structures. The coherent structure and insensitivity to atomic-scale roughness makes it possible to determine the spin distribution by polarized neutron reflectivity, which confirms that the spin structure is collinear. The magnetic reversal behavior of the double superlattices suggests that a realistic model of exchange bias needs to address the process of nucleating local reverse domains.

The magnetic stability of two different interracial exchange coupled systems are investigated using the magneto-optic Kerr effect during repeated reversal of the soft layer magnetization by field cycling up to 10{sup 7} times. For Fe/Cr double-superlattice exchange biased systems, small but rapid initial decay of exchange bias field H{sub E} and the remanent magnetization is observed. Also the Sin-Co/Fe bilayers grown epitaxially with uniaxial in-plane anisotropy show similar decay. However, the H{sub E} of biaxial and random in-plane bilayers, shows gradual decay without large reduction of the magnetization. These different decay behaviors explained by their different microstructure and interracial spin configurations.

Magnetic properties of La 0.9 Sr 0.1 MnO 3 samples prepared by the floating-zone technique have been studied. The compound possesses different crystal structures at different temperatures T : a pseudo-cubic O″-type structure below 100 K, an orthorhombic O′-type between 100 and 320–340 K and a pseudo-cubic O-type structure above 340 K. Below ∼145 K a ferromagnetically ordered state is observed. At low temperatures (∼4 K) the magnetization σ , coercivity H c , differential susceptibility χ 0 in small fields H ⪅ H c , and the forced susceptibility χ Δ in high fields (30–50 kOe) depend on cooling conditions. After zero-field cooling (ZFC), H c =290 Oe, χ 0 is much smaller than the shape susceptibility χ shape , σ (50 kOe)=85.5 emu/g, and χ Δ =5×10 −5 cm 3 /g. The measurements after field cooling (FC) in 50 kOe yield H c χ 0 = χ shape , σ (50 kOe)=96 emu/g, and χ Δ =2.5×10 −5 cm 3 /g. The sample after ZFC is magnetically heterogeneous, while after FC it is nearly homogeneous. In the heterogeneous state, ∼20% of the sample volume is occupied by small precipitates (estimated to be 10–20 nm in size) having zero spontaneous magnetization. However, the precipitates become ferromagnetic in high fields via a metamagnetic transition. The results are interpreted within the framework of a mixed ferromagnetic–antiferromagnetic ground state model.

Shifted hysteresis loops characteristic of the exchange-bias effect between a ferromagnet (F) and an antiferromagnet (AF) are demonstrated in ``double-superlattice'' structures. Utilizing the well-established oscillatory interlayer exchange coupling in Fe/Cr, we have constructed $[\mathrm{F}\mathrm{e}/\mathrm{C}\mathrm{r}{]}^{\mathrm{AF}}/\mathrm{C}\mathrm{r}/[\mathrm{F}\mathrm{e}/\mathrm{C}\mathrm{r}{]}^{F}$ double superlattices where Fe/Cr superlattices with appropriate Cr-spacer thickness represent the F and the AF. The double superlattices are (211)-oriented epitaxial films sputter grown on single-crystal MgO(110) substrates. The AF/F interface is coherent compared to conventional exchange-bias interfaces consisting of dissimilar AF and F phases. Magnetization results show that AF/F exchange coupling affects the nucleation of reverse magnetic domains, and that the magnitude of the exchange-bias field is given directly by the classic formula for collinear spin structures. The collinear spin distribution is confirmed by polarized neutron reflectivity.