Abstract
Microwave-assisted magnetic recording was investigated using a planar write head and exchange-coupled composite (ECC) media. When recording on ECC media using a planar head field distribution and the high frequency field generated by a spin torque oscillator it was possible to switch the media magnetisation into the opposite direction to the head field, i.e. the media effectively had a negative coercive field. The conditions for this effect to occur are discussed.
Highlights
Microwave assisted magnetic recording (MAMR) can be used to reduce the switching field of a magnetic grain
The signal to noise ratio (SNR) of tracks written by the two write heads and using two field generating layer (FGL) chiralities was calculated using the sensitivity function of a magneto-resistive read head with a width of 30 nm and a shield-to-shield spacing of 25 nm
The results are shown in fig. 3 as a function of high frequency (HF) field frequency
Summary
Microwave assisted magnetic recording (MAMR) can be used to reduce the switching field of a magnetic grain. Exchange coupled composite (ECC) grains[2] with soft layer thicknesses between 6 nm and 8 nm displayed this behaviour. It was shown in Ref. 1 that ECC media with a 4 nm hard/5 nm soft structure had the highest switching probability when using “linear” DC fields to switch grains on AC and DC erased media. A planar write head was used to generate a recording field that approximated the linear field in Ref. 1, whilst a spin torque oscillator (STO) was used to generate a localised high frequency (HF) field to assist switching of the grain magnetisation
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