MAMR Frequency Selection on [CoX/Pt]4 Media

Abstract

In microwave-assisted magnetic recording (MAMR), the frequency selection of the assisted microwave magnetic field is important. In this paper, we set up a micromagnetic model of [CoX/Pt]4 media with a different anisotropy configuration to study the frequency selection based on media signal-to-noise ratio (SNR) by the simulation of writing performance. By evaluating each layer’s SNR, we find that the four-layer integrated SNR- $f$ relationship is more influenced by the top two layers, and the interlayer exchange coupling strength plays a dominant role on the consistent SNR- $f$ curve in each media layer. When Hiec = 2000 Oe, the optimum frequency in each layer is coherent; when Hiec = 1000 Oe, the optimum frequency has a 2 GHz difference in four layers. When the average anisotropy field $H_{k}$ is in a range of 19–25 kOe, the integrated optimum frequency $f_{\mathrm {{op{-}all}}}$ with highest media SNR increases versus $H_{\mathbf {k}}$ with a slope of 1.87 GHz/kOe, smaller than the ferromagnetic resonant frequency coefficient of around 3 GHz/kOe, which is beneficial for MAMR applications. With optimized intergrain exchange strength $A_{\mathrm {gb}} = 0.25$ and optimum frequency $f_{\mathrm {op}} = 23$ GHz, an areal writing density limit of 3 Tbit/in2 can be achieved.