Influence of Oblique Writing Field on Writability in Heat-Assisted Magnetic Recording

We analyze the influence of an oblique writing field on writability in 4 Tbpsi shingled heat-assisted magnetic recording employing a stochastic calculation. We confirm the result by employing a micromagnetic simulation. We focus on the mean magnetization reversal number per unit time N- for the medium in the recording direction during writing to analyze the cause. Although erasure-before-write is independent of the writing field angle, erasure-after-write increases as the writing field angle φ measured from the perpendicular increases due to the large N- value after the field writing time. The 1/N- value represents the mean time between stochastically induced magnetization reversals under thermal agitation. We introduce the medium writing time τmed, which is the time range where the N- value is larger than 1 ns^-1. Write-error decreases as the φ value increases, since the 1/N- value becomes shorter and the τmed value becomes longer as the φ value increases. The same bit error rate bER for an oblique writing field can be obtained at a smaller writing field magnitude compared with a writing field perpendicular to the medium plane. Therefore, the minimum bER values are almost the same regardless of φ.