Dr. Howard Zolla
Senior Technologist and Manager,
Western Digital
Date & Time: 13:30 - 14:30, October 17th (Fri), 2025.
Place: 8th Floor Middle Seminar Room, Main Bldg., Sengen.
Ultra Narrow Readers – Challenges & Outlook
Dr. Howard Zolla
Senior Technologist and Manager,
Western Digital
Abstract:
The hard disk drive (HDD) industry is transitioning from conventional, purely magnetic recording to heat assisted magnetic recording (HAMR). Much of the technology underlying this transition focuses on the performance and reliability of optics, plasmonics, write heads and recording media.
Increases in areal density, enabled by HAMR, reduce track pitch more than linear bit length [1] thus requiring read elements which are narrower than any previously produced. Trackwidth reduction plus side reading, head-media spacing loss, mechanical tolerances and process variation will eventually push physical track width to 12nm and below. Today’s magnetic tunnel junction (MTJ) based read elements suffer scaling limitations at these dimensions. Such limitations include increased noise due to higher electrical resistance as well as decreased signal and stability due to reduced physical dimension.
This paper discusses the performance challenges mentioned above as well as patterning challenges associated with fabricating MTJs in the 12nm and narrower regime. This will be followed by a description of a novel read element design based on the inverse spin Hall effect (iSHE). iSHE devices are more complicated to fabricate and utilize since they have separate current and voltage paths requiring four terminals, whereas MTJs require only two. However, we expect such readers will offer improved scaling and performance over MTJ-based devices in the sub-12nm regime.
[1] S. Hernandez et al, “High Areal Density HAMR Demonstration” Presented at TMRC 35, Berkeley, CA (5-7 Aug 2024) paper B1.
Increases in areal density, enabled by HAMR, reduce track pitch more than linear bit length [1] thus requiring read elements which are narrower than any previously produced. Trackwidth reduction plus side reading, head-media spacing loss, mechanical tolerances and process variation will eventually push physical track width to 12nm and below. Today’s magnetic tunnel junction (MTJ) based read elements suffer scaling limitations at these dimensions. Such limitations include increased noise due to higher electrical resistance as well as decreased signal and stability due to reduced physical dimension.
This paper discusses the performance challenges mentioned above as well as patterning challenges associated with fabricating MTJs in the 12nm and narrower regime. This will be followed by a description of a novel read element design based on the inverse spin Hall effect (iSHE). iSHE devices are more complicated to fabricate and utilize since they have separate current and voltage paths requiring four terminals, whereas MTJs require only two. However, we expect such readers will offer improved scaling and performance over MTJ-based devices in the sub-12nm regime.
[1] S. Hernandez et al, “High Areal Density HAMR Demonstration” Presented at TMRC 35, Berkeley, CA (5-7 Aug 2024) paper B1.
(Contact)
Tomoya Nakatani, Magnetic Functional Device Group, CMSM.
E-mail: NAKATANI.Tomoya[at]nims.go.jp
E-mail: NAKATANI.Tomoya[at]nims.go.jp