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We have performed micromagnetic simulations to investigate the magnetic behavior of exchange spring grains for hard disk recording applications. The thickness ratio between magnetically hard and soft layers was varied while the soft layer anisotropy was altered to maintain a suitable energy barrier between opposite magnetization states. The minimum required magnetic field for switching a grain and the corresponding field angle were both significantly reduced in exchange spring material compared with single-phase grains. This could lead to reduced cross-track write errors in hard drive systems and assist the development of magnetic multilayer recording technologies.

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Articles you may be interested in 45 nm wavelength tuning range of an InP/InGaAsP photonic integrated tunable receiver

With a view to better predicting the effects of thermal defocusing within the atmosphere, an experimental simulation set-up has been designed at ONERA. This consists essentially of a vertical airtight cell containing a gas or gas mixture sufficiently absorbing to induce "blooming" of a CO2 laser beam over a distance of about 3 m. A return wind tunnel, integrated within the cell, creates a uniform wind on the beam propagation path ; the wind velocity may be precisely adjusted between 0.1 and 2 m/sec. A rotating drum photometric analyser, associated with a data acquisition and processing unit, provides an automatic sequential exploration of the irradiance model observed at the beam focus. Some characteristic results are presented to illustrate the possibilities offered by the set-up