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Anisotropy Distributions in Nanomagnetic Arrays for Patterned Media

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Exploiting nano-scale magnetic islands

The functionality of nanomagnetic recording devices depends largely on the characteristics of magnetic switching. Novel techniques and instrumentation have opened a new window on nano-scale mechanisms for next-generation storage.

Industrial Technologies

An important measure in characterising magnetic properties of materials is the width of the switching field distribution (SFD), the statistical description of the observed switching fields. A wide SFD indicating a somewhat random reversal of magnetisation is undesirable. Future exploitation of bit patterned media (BPM), the leading candidates for new ultra-high–density data storage paradigms, depends on decreasing their SFD. EU-funded scientists working on the project 'Anisotropy distributions in nanomagnetic arrays for patterned media' (ANDIST) sought to increase understanding in order to make this possible. BPM store bits (0 or 1 according to magnetisation direction) in nano-scale magnetic islands. Storage density increases with decreasing island diameter, paving the way to overcoming current storage limitations. ANDIST developed and utilised several cutting-edge experimental and measurement techniques to elucidate the underlying factors affecting SFD in nano-scale magnetic islands. An innovative approach enabled observation of the magnetic switching of individual nano-scale magnetic islands down to a diameter of 25 micrometres. The experimental results agreed with numerical simulations and theoretical work allowing model predictions down to the smallest islands of less than 10 micrometres in diameter. Work has been published in the esteemed peer-reviewed Journal of Applied Physics. The magneto-optic Kerr effect (MOKE) is a well-established measure of magnetisation properties. Scientists pioneered a new MOKE system enabling measurement of magnetisation reversal mechanisms in small arrays of nano-scale islands with areas as small as 2 micrometres squared. The unprecedented detail now allows correlation of nano-scale structure and physical properties with function. Finally, the team employed small-angle measurement techniques on large-area nano-scale island arrays (thousands of islands) of varying sizes and periodicities. Scientists produced the most statistically meaningful results to date on mean island diameter and diameter variation. ANDIST outcomes form a strong foundation for design of future ultra-high–density storage devices. Results have already been disseminated through numerous papers in various stages of publication as well as at conferences, workshops and invited university talks. New instrumentation and techniques form part of the project's legacy. Strong scientific ties are already forming the basis of new joint research proposals, guaranteeing amplification of the project's momentum.

Keywords

Nano-scale, magnetic islands, nanomagnetic, switching field distribution, bit patterned media, ultra-high–density, data storage, anisotropy distributions, nanomagnetic arrays, storage density, magneto-optic Kerr effect, magnetisation properties

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