Impact of Spin Torque Oscillator Frequency in Microwave-Assisted Magnetic Recording

In this article, we present a systematic modeling investigation for some important physical insights in microwave-assisted magnetic recording (MAMR). Specifically, the characteristics of the effective write field in the presence of the ac field generated by the embedded spin torque oscillator (STO) is analyzed in terms of field strength and field-gradient gain for recording, as well as the enhancement of reverse erasure field. It is found that the rotating frequency of the field generating layer (FGL) of the STO plays a very important role. The effective write field enhancement for both recording and erasure due to the rotating ac field increase with increasing the ac field frequency with a rate close to 1 T per 28 GHz. Either the recording field gain or erasure field enhancement rolls off at high frequencies. The roll-off frequency for the recording field gain is significantly higher, approximately 20 GHz, than that for erasure field enhancement, leaving a broader frequency range for the ac field over which substantial gains for the recording field strength and gradients can be obtained while avoiding any erasure field enhancement. The understanding also provides guidelines for both head and media designing.