Self-organized Co/Pt nanoparticulate arrays offer a novel approach to fabricating magnetic recording media with the potential for supporting Terabit/in.2 recording densities. Protein-derived Co/Pt nanoparticles are prepared within apoferritin from aqueous reactants, with synthesis conditions controlling grain size, structure, and composition. Smooth films on glass disk substrates are produced by either spin coating or dip coating from aqueous dispersions of the precursor material. Films are typically annealed at 590 °C for 60 min with a 19 kPa (190 mBar) partial pressure of H2 to form the L10 phase. By varying the annealing conditions we are able to produce coercivities in the range of 500–8000 Oe. Electrical testing of Co/Pt nanoparticulate media using a contact test recorder shows that these nanoparticle films are capable of sustaining recording densities of more than 12.6 Gbits/in.2 (143.6 kfci, kilo flux changes per inch). In this article we will present results from finished films with regard to film structure, magnetic properties, and recording capabilities.

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We report the first use of direct detection for recording electron backscatter diffraction patterns. We demonstrate the following advantages of direct detection: the resolution in the patterns is such that higher order features are visible; patterns can be recorded at beam energies below those at which conventional detectors usefully operate; high precision in cross-correlation based pattern shift measurements needed for high resolution electron backscatter diffraction strain mapping can be obtained. We also show that the physics underlying direct detection is sufficiently well understood at low primary electron energies such that simulated patterns can be generated to verify our experimental data. DOI: 10.1103/PhysRevLett.111.065506 PACS numbers: 61.05.JÀ, 07.78.+s, 68.37.Hk Electron backscatter diffraction (EBSD) is a scanning electron microscope (SEM) based method in which diffraction of low-energy-loss electrons as they exit through the topmost few tens of nanometers leads to Kikuchi diffraction. In most EBSD studies the incident electron beam is stepped across a grid of points on the sample surface and the EBSD patterns analyzed in an automated way to determine crystal phase, orientation, or lattice strain variation. The EBSD method has evolved rapidly over the last two decades [1][2][3][4][5]. Most research has been directed to the application of this versatile tool to an ever increasing array of problems in materials characterization but the analysis methods themselves have also advanced, notably in three dimensional imaging using focused ion beam (FIB)-SEM [6-9] and in strain mapping [10][11][12][13][14]. However, the detector technology used to record EBSD patterns has essentially remained unchanged for over a decade and now limits performance in several application areas, such as strain resolution and low dose mapping, and prevents the development of new areas.The earliest EBSD patterns were recorded on film either exposed directly to the electrons in the chamber [15][16][17], or indirectly imaging a phosphor screen using a camera outside the vacuum [18]. Subsequently, these were replaced by various image intensified cameras giving the convenience of a live image of the pattern at the scintillator but with degraded pattern quality compared to that recorded using film [19]. Subsequently, scintillator coupled CCDs were introduced in the early 1990s [20,21]. In a limited number of examples tapered fiber-optic bundles have been used to couple the CCD to the scintillator with good results [20] but the alternative optical lens coupling has been adopted in the vast majority (> 95%) of instruments currently in use. Departures from these detection schemes have included an investigation of microchannel plates [22] and the adoption of a retarding electrostatic field for energy filtering [23].In other fields there have been significant advances in detectors directly exposed to the imaging beam for the detection of x rays [24,25] and medium energy electrons [26][27][28][29]. The current development of TEM instr...

Routine EBSD analysis typically applies a 2D Hough transform technique. This requires collection and background correction of the Kikuchi pattern. A Hough transform is applied to highlight and locate the Kikuchi bands. These bands are revealed as local peaks in the resulting Hough space and their corresponding maxima are found automatically, locating the position and direction of the Kikuchi bands and the corresponding diffraction planes. In this primary band detection routine each maximum is represented by a (rho, theta) position in Hough space. In the subsequent indexing the interplanar angles are matched against a database of known phases, and the phase and orientation of the crystal is determined.Precision and accuracy of this primary band detection is essentially limited by the precision of identifying and locating the Kikuchi bands, which is in turn limited by the Hough transform. Therefore, the precision in the orientation measurement can be improved by increasing the resolution of the Hough transform and the resulting Hough space; however this results in a significant increase in calculation time. In addition, the Hough transform assumes that the Kikuchi bands are straight lines, whereas in reality the Kikuchi bands in a pattern have varying widths and curved (hyperbolic) edges. Therefore the conventional 2D Hough transform method introduces a systematic error which cannot be overcome through increased Hough space resolution.An alternative method [1] describes modifying the Hough transform so that it identifies hyperbolic curves rather than straight lines. This modified Hough transform applies a 3D space where the third dimension is given by the hyperbola variable. This method eliminates the systematic error of the conventional Hough, but it involves a large three dimensional calculation which makes it computationally slow. This paper will present a new analysis routine for EBSPs, which improves the accuracy of band detection and is achievable in real time applications. The method uses the primary band detection as its foundation, and then applies an iterative secondary band detection to improve upon the accuracy of the primary band detection.This accurate determination of band positions enables the calculation of a more accurate orientation matrix and thus improves general EBSD analysis, e.g. ability to distinguish between two phases with a very close crystal structure; or in characterizing low angle boundaries. In addition, this refinement will deliver an accurate solution when the primary band detection is impaired by the presence of excess and deficit lines.The mean angular deviation (MAD) is a measure of the fit between the Kikuchi bands in the measured pattern and the solution. It can be used as figure of merit for the accuracy of band detection and therefore also for phase identification. Many applications of EBSD consider misorientation which is also related to the accuracy and precision of band detection. 724

Magnetoferritin nanoparticles consist of ferrimagnetic magnetite–maghemite surrounded by a protein shell. Thermal relaxation data for both agglomerated and well-separated magnetoferritin show clear Tln(t/τ0) scaling, thereby permitting a direct evaluation of the influence of magnetostatic interactions on the effective energy barrier distribution for magnetic reversal. For agglomerated magnetoferritin, the effect of the interactions is to broaden the distribution and shift its peak to lower energies, in contrast to the peak in the zero-field-cooled susceptibility, which moves to higher energies. Our result is in good agreement with earlier theoretical predictions (Iglesias and Labarta 2004 Phys. Rev. B 70 144401).