Optimal write head design for perpendicular magnetic recording

Abstract

Perpendicular Magnetic Recording (PMR) [1] is widely commercialized but the areal density gains for PMR are slowing down. The writer is a very important component of the magnetic recording system with many parameters that need to be optimized. The writing performance depends on many parameters and there are many metrics that could be used to predict the performance, in particular, the writer field strength and the write field gradient are two important such metrics. However, exactly how these intermediate metrics translate into areal density gain is a complex process involving improvement to the SNR and BER. Therefore, we adopt an approach to search for the optimal solution of the write head design based on the maximization of the signal-to-noise ratio (SNR) and the minimization of the bit error rate (BER) via micromagnetic simulations the grain-flipping probability (GFP) model [2] and channel simulation. We select six variables as the design parameters in the write head. An initial screen testing is performed to decide the nominal values of these parameters and their variations. The design of experiments (DOE) is conducted by applying an orthogonal array (OA) [3] and LLG-based micromagnetic simulations are carried out to obtain the magnetization distributions in the recording media for each head design. These magnetization distributions are then used to train the corresponding grain-flipped probability model (GFPs). The SNRs and BERs are obtained from processing the GFP model output with a software channel. The Taguchi method [3] is used to identify the optimal solution by maximizing the SNRs and minimizing the BERs. Using the Taguchi method, we predict the SNR and the BER at the optimal head design and finally, the verification is performed by micromagnetic simulation, GFP model, SNR characterization and BER calculation for the optimal design.