Requirements for soft magnetic underlayer (SUL)—Micromagnetic simulations of single-pole-type write heads and SUL systems

Landau-Lifshitz-Gilbert micromagnetic models were used to analyze the head field distributions and high-frequency responses for various soft magnetic underlayer thicknesses (t-SUL) and saturation magnetization flux densities (B_s) of single-pole-type (SPT) head-SUL systems. It was found that B_s of 10-12 kG and t-SUL of 30-45 nm would be sufficient for the examined head and perhaps for most next generation head-SUL systems. Antiferromagnetic coupling in the SUL affects the head and SUL magnetization and, eventually, the head field. With regard to the head magnetization response, it was found that the magnetization under the coil responded first, while the response at the main pole tip was quite slow, even compared with the head field. The main pole tip of the head was fully saturated and the main pole yoke was almost saturated, while the SUL was not saturated in the examined head-SUL system.