Abstract
Several studies have confirmed that current-perpendicular-to-the-plane giant magnetoresistance (CPP-GMR) technology is appropriate for next-generation read sensors for ultrahigh areal densities (ADs) of data storage applications. Since the physical dimension of the read sensor is a crucial factor for developing the reader to overcome its limitations, this paper proposes an optimal sizing prediction of the CPP-GMR read heads for ADs of 1-4 Tb/in2. Micromagnetic modelling was performed in the simulations. The appropriate length of the stripe height (SH) and the read width (RW) of the readers was estimated based on a consideration of sensor outputs including the readback signal, asymmetry parameter, dibit response and power spectral density (PSD) profile. It was found that a variation of SH and RW lengths had an influential impact on the readback signal waveform. Those affectations were further characterized through the echoes of dibit response showing that shortening the SH length or increasing the RW length could improve the resolution and reduce the distortion occurring in the readback signal. Moreover, the PSD profile indicated that the reader operation became more stable at shorter SH lengths or longer RW lengths. The head response spectrum was also examined. In addition, the magnitude of the bias current was studied in relation to the head response. Lastly, the optimal physical dimension (SH $\times $ RW) of the CPP-GMR readers for ADs of 1-4 Tb/in2 was predicted to be ( $40 \times 48$ ) nm, ( $28 \times 29$ ) nm, ( $25 \times 26$ ) nm and ( $19 \times 20$ ) nm, respectively. The results can be utilized to design the CPP-GMR sensors at ultrahigh magnetic recording capacities.
Highlights
As the areal density (AD) of the hard disk drive (HDD) is expected to reach 10 Tb/in2 in the coming decade, challenges in developing the magnetic recording heads to deal with a shrinking of media bit size have been extensively researched [1]–[3]
We firstly evaluated the optimal sizing of the current-perpendicularto-the-plane giant magnetoresistance (CPP-GMR) reader for an AD of 1 Tb/in2 based on a consideration of reader outputs including the readback signal, dibit response, asymmetry parameter and the power spectral density (PSD) profile
The limitations that the read width (RW) length has to be less than the 0.95 × media track width as well as the stripe height (SH) should not exceed 1.1 × RW were included [37]
Summary
As the areal density (AD) of the hard disk drive (HDD) is expected to reach 10 Tb/in in the coming decade, challenges in developing the magnetic recording heads to deal with a shrinking of media bit size have been extensively researched [1]–[3]. P. Khunkitti et al.: Optimal Sizing of CPP-GMR Read Sensors for Magnetic Recording Densities of 1–4 Tb/in from adjacent tracks [18]. To predict the optimal sizing of the CPP-GMR read heads for ADs of 1-4 Tb/in, an appropriate length of the SH and RW for all ADs was evaluated under the condition the system is based on the conventional reader operation, as well as conventional perpendicular media. The possible varying range of SH and RW was limited based on the condition that the magnetization of the head could be ±30◦ tilt while operating Beyond this considered range, the magnetization of the free layer was not able to be stabilized with ±30◦ tilted during an operation due to an incompatibility of the hard-bias field and the anisotropy field. It was noted that the length of SH or RW was individually adjusted for all cases of investigations, so that the length of RW was fixed during an adjustment of the SH length and vice versa
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