Areal Density Capability of Dual-Structure Media for Microwave-Assisted Magnetic Recording

In this article, we investigate the areal density capability (ADC) of dual-structure media for microwave-assisted magnetic recording. The recording medium consists of two, discrete exchange-coupled composite (ECC) recording structures, each with hard and soft magnetic layers. The magnetic properties of the hard and soft layers of each ECC structure were optimized using the response surface methodology. The optimization parameters included hard and soft layer uniaxial anisotropy, the strength of exchange coupling between the hard and soft layers and the frequency of the spin torque oscillator (STO). Next, the ADC was calculated for a range of STO widths. The results showed that the use of narrower STOs increased the ADC of the top recording structure, but made little difference to the ADC of the lower recording structure. To validate the ADC values a grain switching probability (GSP) model was developed which took account of the magnetization of both structures. The GSP model was used to generate longer readback waveforms for use in a software read channel model, from which the bit error rate and user areal density were derived.