Young-hun Im

Optimum design rule of hysteresis loop for ultrahigh density recording in single-layered perpendicular media

Micromagnetic studies have been performed to find optimum shape of hysteresis loop in a single-layered perpendicular medium for ultrahigh density recording. A good index that was inversely proportional to signal-to-noise ratio (SNR) was developed. By using this index, we found the optimum loop shape should have terms of the ratio of nucleation field to coercivity within -0.4 to -0.6, the loop slope within 2 to 4, and the ratio of grain thickness to grain diameter larger than 2.5.

Head design scheme for perpendicular recording with single layered media

For ultra high areal recording density, we suggest the perpendicular recording scheme with ring head and single layered media for easy implementation. To improve the perpendicular head field and its gradient, conventional ring head is modified by cutting the top pole edge. Head field was calculated with nonlinear finite element method. The write process was simulated with micromagnetics using the calculated head field of two heads (original and modified) at each magnetic grain of recording disk, instead of using Karlqvist head field. Both simulated and measured MFM images show that the transition of modified head is clearer than original one. Also, TAA and SNR of modified head are higher than results of original head. With simple modification, currently used ring head can be easily applied to high density perpendicular recording HDD system.

Recording physics of perpendicular recording with single layered medium and ring head

In this article, the recording physics of a ring head with a single layered perpendicular medium (Ring/SL) is studied and the results are compared with a single pole head with a double layered perpendicular medium (SPT/DL) by using various simulations and experiments. The Ring/SL has much lower effective medium coercivity than the SPT/DL due to the substantial longitudinal field component of ring head and the incoherent rotation mode of medium magnetizations. Furthermore, switching time of the Ring/SL is estimated as only 10%∼30% of the SPT/DL. In the Ring/SL, the head field gradient of 40 Oe/nm is enough for maximizing SNR. The Ring/SL shows very low noise characteristics especially at high linear density. The signal output of the Ring/SL is smaller than the SPT/DL, but it is large enough to be detected. Therefore, it can be concluded that the combination of single layered perpendicular medium and ring head is highly promising for ultrahigh density recording.

Dynamic recording property simulations of perpendicular magnetic recording with ring head and single layered media

Summary form only given. Perpendicular magnetic recording is one of the promising candidates of the next-generation magnetic recording system for ultra high recording density. Perpendicular magnetic recording with a ring head and single layered media has strong merits because of its easy implementation in conventional hard disk technology. In spite of these small changes, the perpendicular recording system shows quite different dynamic recording behavior when compared with the longitudinal system because the media demagnetization field has an opposite effect.