38 research outputs found
First order reversal curves and intrinsic parameter determination for magnetic materials: limitations of hysteron-based approaches in correlated systems
No full textThe generic problem of extracting information on intrinsic particle properties from the whole class of interacting magnetic fine particle systems is a long standing and difficult inverse problem. As an example, the Switching Field Distribution (SFD) is an important quantity in the characterization of magnetic systems, and its determination in many technological applications, such as recording media, is especially challenging. Techniques such as the first order reversal curve (FORC) methods, were developed to extract the SFD from macroscopic measurements. However, all methods rely on separating the contributions to the measurements of the intrinsic SFD and the extrinsic effects of magnetostatic and exchange interactions. We investigate the underlying physics of the FORC method by applying it to the output predictions of a kinetic Monte-Carlo model with known input parameters. We show that the FORC method is valid only in cases of weak spatial correlation of the magnetisation and suggest a more general approach
Lattice-Mismatch-Induced Oscillatory Feature Size and Its Impact on the Physical Limitation of Grain Size
No full textWe find that the misfit strain may lead to the oscillatory size distributions of heteroepitaxial nanostructures. In heteroepitaxial FePt thin films grown on single-crystal MgO substrate, -oriented mazelike and granular patterns with "quantized" feature sizes are realized in scanning-electron-microscope images. The physical mechanism responsible for the size oscillations is related to the oscillatory nature of the misfit strain energy in the domain-matching epitaxial FePt/MgO system, which is observed by transmission electron microscopy. Based on the experimental observations, a model is built and the results suggest that when the FePt island sizes are an integer times the misfit dislocation period, the misfit strain can be completely canceled by the misfit dislocations. With applying the mechanism, small and uniform grain is obtained on the TiN (200) polycrystalline underlayer, which is suitable for practical application. This finding may offer a way to synthesize nanostructured materials with well-controlled size and size distribution by tuning the lattice mismatch between the epitaxial-grown heterostructure
Measurement of the anisotropy field dispersion in perpendicular media using complex transverse AC susceptibility
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Preparation and properties of perpendicular CoPt magnetic nanodot arrays patterned by nanosphere lithography
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