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Describes the after-effect measurements performed on arrays of isolated ultrathin monocrystalline disk-shaped iron dots with inplane magnetization. Advantages of magnetic after-effect measurements; Sample fabrication and basic properties; Experimental protocol for magnetic after-effect measurements.

We report the fabrication of self-organized arrays of Fe nanostripes with a lateral period of 3.5 nm by sequential deposition of Fe and Ag on Mo(110). The wires display a strong in-plane uniaxial magnetic anisotropy along their length and are superparamagnetic above TB=185±15 K. The large value of nucleation volumes, which is inferred from the analysis of the thermal dependence of coercivity below TB, suggests the existence of interactions between the wires. [ABSTRACT FROM AUTHOR]

Abstract: We report a detailed magnetic study of a new type of self-organized nanowires discussed briefly previously [B. Borca et al., Appl. Phys. Lett. 90 (2007) 142507]. The templates, prepared on sapphire wafers in a kinetically limited regime, consist of uniaxially grooved W(110) surfaces, with a lateral period here tuned to 15nm. Fe deposition leads to the formation of (110) 7nm-wide wires located at the bottom of the grooves. The effect of capping layers (Mo, Pd, Au, Al) and underlayers (Mo, W) on the magnetic anisotropy of the wires was studied. Significant discrepancies with figures known for thin flat films are evidenced and discussed in terms of step anisotropy and strain-dependent surface anisotropy. Demagnetizing coefficients of cylinders with a triangular isosceles cross-section have also been calculated, to estimate the contribution of dipolar anisotropy. Finally, the dependence of magnetic anisotropy with the interface element was used to tune the blocking temperature of the wires, here from 50 to 200K. [Copyright &y& Elsevier]

Abstract: Homoepitaxy of W(110) and Mo(110) is performed in a kinetically-limited regime to yield a nanotemplate in the form of a uniaxial array of hills and grooves aligned along the [001] direction. The topography and organization of the grooves were studied with RHEED and STM. The nanofacets, of type {210}, are tilted ∼18° away from (110). The lateral period could be varied from 4 to 12nm by tuning the deposition temperature. Magnetic nanowires were formed in the grooves by deposition of Fe at 150°C on such templates. Fe/W wires display an easy axis along [001] and a mean blocking temperature T B ≈100K. [Copyright &y& Elsevier]

We propose improvements and extensions to an analytical model of magnetization reversal in ultrathin flat dots and stripes with in-plane uniaxial anisotropy. Owing to the localized character of nucleation volumes in hard magnetic materials, we use the concept of edge demagnetizing torque, where all demagnetizing effects are applied at the dot''s edge. The magnetization state and the reversal field &htilde;r are predicted as a function of magnetization, dot thickness and in-plane edge orientation. An excellent agreement is found with numerical simulations. An approximate but accurate scaling law is proposed for an easy computation of &htilde;r. The model is shown to be valid for dots thinner than both exchange length and wall width, and lateral size well above each of these lengths. [Copyright &y& Elsevier]

A kinetic analysis of Fe islands growth on Mo(1 1 0) in the sub-monolayer range as a function of temperature is presented for the pulsed laser deposition (PLD) epitaxial technique. It has allowed us to determine the corresponding diffusion barrier Ed=0.1±0.05 eV and the diffusion attempt frequency ν0=8×1011±1 Hz. Numerical integration of the standard kinetic differential equations is used to describe the specificity of the pulsed character of PLD. Good agreement is found with experimental results. A comparison to reported molecular beam epitaxy (MBE) sub-monolayer growth of Fe at 300 K is also considered. The PLD technique is demonstrated to lead to an increase of the diffusion rate by 4 orders of magnitude, presumably as a consequence of the higher energy of the impinging species. Incidentally, this increase of diffusion rate is compensated by the large instantaneous deposition flux leading to identical densities using MBE or PLD for Fe/Mo(1 1 0) at 300 K. [Copyright &y& Elsevier]

We report various experiments that cast some light on the growth process of self-organized dots and vertical Co pillars on Au(1 1 1). We first report grazing incidence small angle X-ray scattering (GISAXS) on Co dots and films, that allowed us to perform a crystallographic study of the order in the self-organized array, and also yielded a statistical view of the coalescence process. We then report scanning tunneling microscopy (STM) and spectroscopy (STS) images performed during the course of vertical growth. Details about the atomic growth process and the possible influence of the growth technique used are reported. [Copyright &y& Elsevier]

We report the fabrication of epitaxial nanometer-thick magnetic structures, self-organized on surface reconstructions [Co/Au (1 1 1) pillars] and atomic step arrays [Fe/Mo (1 1 0) stripes]. Due to their high volume, these structures are remanent at room temperature, whereas conventional self-organized flat systems obtained in the sub-monolayer deposition range are superparamagnetic down to low temperatures. [Copyright &y& Elsevier]

We have developed and characterized the structure and composition of nanometers-thick solid-solution epitaxial layers of (V,Nb) on sapphire [formula], displaying a continuous lateral gradient of composition from one to another pure element. Further covered with an ultrathin pseudomorphic layer of W, these provide a template for the fast combinatorial investigation of growth or physical properties depending of strain. [ABSTRACT FROM AUTHOR]

The authors have self-organized versatile magnetic nanowires, i.e., with variable period and adjustable magnetic anisotropy energy (MAE). First, using the kinetic roughening of W(110), uniaxial templates of trenches were grown on commercial sapphire wafers. Unlike most templates used for self-organization, those have a variable period; 4–12 nm are demonstrated here. Fe deposition then results in the formation of wires in the trenches. The magnitude of MAE could be engineered up or down by changing the capping layer or underlayer, in turn affecting the mean superparamagnetic temperature, raised to 175 K so far. [ABSTRACT FROM AUTHOR]

We have fabricated 5-nm-high Fe(110) stripes by self-organized (SO) growth on a slightly vicinal R(110)/Al[sub 2]O[sub 3](1120) surface (R=Mo,W). Remanence, coercivity, and domain patterns were observed at room temperature. This contrasts with conventional SO epitaxial systems, that are superparamagnetic or even nonmagnetic at RT due to their flatness. Our process should help to overcome superparamagnetism without compromise on the lateral size if SO systems are ever to be used in applications. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Magnetic domain walls (DWs) in nanostructures are low-dimensional objects that separate regions with uniform magnetisation. Since they can have different shapes and widths, DWs are an exciting playground for fundamental research, and became in the past years the subject of intense works, mainly focused on controlling, manipulating, and moving their internal magnetic configuration. In nanostrips with in-plane magnetisation, two DWs have been identified: in thin and narrow strips, transverse walls are energetically favored, while in thicker and wider strips vortex walls have lower energy. The associated phase diagram is now well established and often used to predict the low-energy magnetic configuration in a given magnetic nanostructure. However, besides the transverse and vortex walls, we find numerically that another type of wall exists in permalloy nanostrips. This third type of DW is characterised by a three-dimensional, flux closure micromagnetic structure with an unusual length and three internal degrees of freedom. Magnetic imaging on lithographically-patterned permalloy nanostrips confirms these predictions and shows that these DWs can be moved with an external magnetic field of about 1 mT. An extended phase diagram describing the regions of stability of all known types of DWs in permalloy nanostrips is provided. [ABSTRACT FROM AUTHOR]

We investigate numerically the transverse versus vortex phase diagram of head-to-head domain walls in Co/Cu/Py spin valve nano-stripes (Py: permalloy), in which the Co layer is mostly single domain while the Py layer hosts the domain wall. The range of stability of the transverse wall is shifted towards larger thickness compared to single Py layers, due to a magnetostatic screening effect between the two layers. An approached analytical scaling law is derived, which reproduces faithfully the phase diagram. [ABSTRACT FROM AUTHOR]

Recent studies in three-dimensional spintronics propose that the Œrsted field plays a significant role in cylindrical nanowires. However, there is no direct report on its impact on magnetic textures. Here, we use time-resolved scanning transmission x-ray microscopy to image the dynamic response of magnetization in cylindrical Co30Ni70 nanowires subjected to nanosecond Œrsted field pulses. We observe the tilting of longitudinally magnetized domains toward the azimuthal Œrsted field direction and create a robust model to reproduce the differential magnetic contrasts and extract the angle of tilt. Furthermore, we report the compression and expansion, or breathing, of a Bloch-point domain wall that occurs when weak pulses with opposite signs are applied. We expect that this work lays the foundation for and provides an incentive to further studying complex and fascinating magnetization dynamics in nanowires, especially the predicted ultra-fast domain wall motion and associated spin wave emissions. [ABSTRACT FROM AUTHOR]

Ordered arrays of magnetic nanowires are commonly synthesized by electrodeposition in nanoporous alumina templates. Due to their dense packing, strong magnetostatic interactions prevent the manipulation of wires individually. Using atomic layer deposition we reduce the diameter of the pores prior to electrodeposition. This reduces magnetostatic interactions, yielding fully remanent hysteresis loops. This is a first step toward the use of such arrays for magnetic racetrack memories. [ABSTRACT FROM AUTHOR]

X-ray photoelectron emission microscopy in combination with x-ray magnetic circular dichroism is used to investigate the influence of an applied magnetic field on Néel caps (i.e., surface terminations of asymmetric Bloch walls). Self-assembled micron-sized Fe(110) dots displaying a moderate distribution of size and aspect ratios serve as model objects. Investigations of remanent states after application of an applied field along the direction of Néel-cap magnetization give clear evidence for the magnetization reversal of the Néel caps around 120 mT, with a ±20 mT dispersion. No clear correlation could be found between the value of the reversal field and geometrical features of the dots. [ABSTRACT FROM AUTHOR]

We report several procedures for the robust nucleation of magnetic domain walls in cylindrical permalloy nanowires. Specific features of the magnetic force microscopy (MFM) contrast of such wires are discussed, to avoid the misinterpretation of the magnetization states. The domain walls moved under quasistatic magnetic fields in the range 0.1-10mT, as evidenced by MFM at remanence at different stages of their motion. [ABSTRACT FROM AUTHOR]

Provides soft x-ray resonant magnetic reflectivity measurements of thin films and multilayers. How linear polarized photons were used in the measurement of the thin films and multilayers in a transverse geometry; Quantitative examination of the magnetic properties of thin films and multilayers.

During limb development, the spatio-temporal expression of sonic hedgehog ( SHH) is driven by the Zone of polarizing activity Regulatory Sequence ( ZRS), located 1 megabase upstream from SHH. Gain-of-function mutations of this enhancer, which cause ectopic expression of SHH, are known to be responsible for congenital limb malformations with variable expressivity, ranging from preaxial polydactyly or triphalangeal thumbs to polysyndactyly, which may also be associated with mesomelic deficiency. In this report, we describe a patient affected with mirror-image polydactyly of the four extremities and bilateral tibial deficiency. The proband's father had isolated preaxial polydactyly type II ( PPD2). Using Sanger sequencing, a ZRS point mutation (NC_000007.14, g. 156584153A>G, UCSC, Build hg.19) was only identified in the patient. However, pyrosequencing analysis enabled the detection of a 10% somatic mosaic in the blood and saliva from the father. To our knowledge, this is the first description of a ZRS mosaic mutation. This report highlights the complexity of genotype-phenotype correlation in ZRS-associated syndromes and the importance of detecting somatic mosaicism for accurate genetic counselling. [ABSTRACT FROM AUTHOR]

Magnetic frustration effects in artificial kagome arrays of nanomagnets with out-of-plane magnetization are investigated using magnetic force microscopy and Monte Carlo simulations. Experimental and theoretical results are compared to those found for the artificial kagome spin ice in which the nanomagnets have inplane magnetization. In contrast with what has been recently reported, we demonstrate that long-range (i.e., beyond nearest-neighbor) dipolar interactions between the nanomagnets cannot be neglected when describing the magnetic configurations observed after demagnetizing the arrays using a field protocol. As a consequence, there are clear limits to any universality in the behavior of these two artificial frustrated spin systems. We provide arguments to explain why these two systems show striking similarities at first sight in the development of pairwise spin correlations. [ABSTRACT FROM AUTHOR]

A correction is presented for a graph in the article "Reduction of magnetostatic interactions in self-organized arrays of nickel nanowires using atomic layer deposition" which is in a 2011 issue of this journal.

Abstract: We investigated to which extent a uniaxially-strained Au(111) surface, thereby displaying linear reconstructions, may be used as a template for the growth of elongated nanostructures. Cobalt has been used as a deposition material and two routes have been followed satisfactorily. The first one consists of the control of diffusion through the temperature of deposition. The second one consists of a first step of platinum seeding in the reconstruction, followed by cobalt deposition with nucleation on the platinum seeds. [Copyright &y& Elsevier]

We have used time-resolved x-ray photoemission electron microscopy to investigate the magnetization dynamics induced by nanosecond current pulses in NiFe/Cu/Co nanostripes. A large tilt of the NiFe magnetization in the direction transverse to the stripe is observed during the pulses. We show that this effect cannot be quantitatively understood from the amplitude of the Oersted field and the shape anisotropy. High-frequency oscillations observed at the onset of the pulses are attributed to precessional motion of the NiFe magnetization about the effective field. We discuss the possible origins of the large magnetization tilt and the potential implications of the static and dynamic effects of the Oersted field on current-induced domain-wall motion in such stripes. [ABSTRACT FROM AUTHOR]

Abstract: We present a study of the magnetization reversal dynamics in ultrathin Au/Co/Au films with perpendicular magnetic anisotropy, for a Co thickness of 0.5, 0.7 and 1nm. In these films, the magnetization reversal is dominated by domain nucleation for t Co=0.5, 0.7nm and by domain wall propagation for tCo=1nm. The prevalence of domain nucleation for the thickness range 0.5–0.7nm is different from results reported in the literature, for the same system and for the same thickness range, where the magnetization reversal took place mainly by domain wall motion. We attribute this difference to the effect of roughness of the Au buffer layer on the morphology of the magnetic layer. [Copyright &y& Elsevier]

Abstract: The growth mode, magnetic and magneto-optical properties of epitaxial Au/Co/Au(111) ultrathin trilayers grown by pulsed-laser deposition (PLD) under ultra-high vacuum are presented. Sapphire wafers buffered with a single-crystalline Mo(110) buffer layer were used as substrates. Owing to PLD-induced interfacial intermixing at the lower Co/Au(111) interface, a close-to layer-by-layer growth mode is promoted. Surprisingly, despite this intermixing, ferromagnetic behavior is found at room temperature for coverings starting at 1 atomic layer (AL). The films display perpendicular magnetization with anisotropy constants reduced by 50% compared to TD-grown or electrodeposited films, and with a coercivity more than one order of magnitude lower . The magneto-optical (MO) response in the low Co thickness range is dominated by Au/Co interface contributions. For thicknesses starting at 3 AL Co, the MO response has a linear dependence with the Co thickness, indicative of a continuous-film-like MO behavior. [Copyright &y& Elsevier]

Abstract: A finite element formalism is proposed to solve the dynamic micromagnetic equations. To estimate the validity and the accuracy of this finite element approach, the results of two bidimensional test cases are compared with a finite difference approach. [Copyright &y& Elsevier]

A nonconventional finite element formalism is proposed to solve the dynamic Landau-Lifshitz-Gilbert micromagnetic equations. Two bidimensional test problems are treated to estimate the validity and the accuracy of this finite element approach. [ABSTRACT FROM AUTHOR]

Magnetic properties of nanometer-thick Co films intercalated at the graphene/Ir(111) interface are investigated using spin-polarized low-energy electron microscopy and Auger electron spectroscopy. We show that the graphene top layer promotes perpendicular magnetic anisotropy in the Co film underneath, even for relatively thick intercalated deposits. The magnetic anisotropy energy is significantly larger for the graphene/Co interface than for the free Co surface. Hybridization of the graphene and Co electron orbitals is believed to be at the origin of the observed perpendicular magnetic anisotropy. [ABSTRACT FROM AUTHOR]

While the usual approach to tailor the behavior of condensed matter and nanosized systems is the choice of material or finite-size or interfacial effects, topology alone may be the key. In the context of the motion of magnetic domain walls (DWs), known to suffer from dynamic instabilities with low mobilities, we report unprecedented velocities >600 m/s for DWs driven by spin-transfer torques in cylindrical nanowires made of a standard ferromagnetic material. The reason is the robust stabilization of a DW type with a specific topology by the Œrsted field associated with the current. This opens the route to the realization of predicted new physics, such as the strong coupling of DWs with spin waves above >600 m/s. [ABSTRACT FROM AUTHOR]

Domain wall propagation in modulated-diameter cylindrical nanowires is a key phenomenon to be studied with a view to designing three-dimensional magnetic memory devices. This paper presents a theoretical study of transverse domain wall behavior under the influence of a magnetic field within a cylindrical nanowire with diameter modulations. In particular, domain wall pinning close to the diameter modulation was quantified, both numerically, using finite element micromagnetic simulations, and analytically. Qualitative analytical model for gently sloping modulations resulted in a simple scaling law which may be useful to guide nanowire design when analyzing experiments. It shows that the domain wall depinning field value is proportional to the modulation slope. [ABSTRACT FROM AUTHOR]

Shadow x-ray magnetic circular dichroism photoemission electron microscopy is a recent technique, in which the photon intensity in the shadow of an object lying on a surface may be used to gather information about the three-dimensional magnetization texture inside the object. Our purpose here is to lay the basis of a quantitative analysis of this technique. We first discuss the principle and implementation of a method to simulate the contrast expected from an arbitrary micromagnetic state. Textbook examples and successful comparison with experiments are then given. Instrumental settings are finally discussed, having an impact on the contrast and spatial resolution: photon energy, microscope extraction voltage and plane of focus, microscope background level, electric-field related distortion of three-dimensional objects, Fresnel diffraction, or photon scattering. [ABSTRACT FROM AUTHOR]