Write field asymmetry in perpendicular magnetic recording

Abstract

We present a systematic study of write field asymmetry by using micromagnetic modeling for a perpendicular magnetic recording (PMR) writer structure. Parameters investigated include initial magnetization condition, write current amplitude, write current frequency, and initial write current polarity. It is found that the write current amplitude and frequency (data rate) are the dominant factors that impact the field asymmetry. Lower write current amplitude and higher write current frequency will deteriorate the write field asymmetry, causing recording performance (such as bit error rate) degradation.

Time resolved imaging of magnetization dynamics in hard disk writer yokes excited by bipolar current pulses

“…Increased data rates in perpendicular magnetic recording 1 (PMR) require the magnetization within the recording head to respond to the driving field sufficiently quickly that erase after write 2 (EAW) phenomena are avoided. Previous studies [3][4][5][6][7][8][9] have addressed the rise time and remnant value of the write field at the pole tip. However, magnetic flux 10 is delivered to the confluence and tip regions from the yoke by a process known as "flux beaming."…”

“…All of these studies were carried out with unipolar pulses, while a hard disk drive employs a bipolar waveform with positive and negative phases of similar amplitude. 9 Therefore in this study, to afford more direct comparison with performance of the writer in a hard disk drive, bipolar pulses have been used in time resolved scanning Kerr microscopy 15 measurements performed on a partially built writer with a NiFe/CoFe(100 nm)/Ru/NiFe/CoFe(100 nm) synthetic antiferromagnetic (SAF) yoke structure.…”