Robert E. Fontana

All-Metal Current-Perpendicular-to-Plane Giant Magnetoresistance Sensors for Narrow-Track Magnetic Recording

Read heads using current-perpendicular-to-plane (CPP) giant magnetoresistance sensors have been fabricated and tested under high-density recording conditions. A magnetoresistance of 5.5% and shield-to-shield spacing of 45 nm have been achieved by using an all-metal single-spin-valve with Heusler-alloy-based free and reference magnetic layers. Read heads with magnetic read widths ~45 nm were tested on perpendicular media, resulting in signals above 1 mV and signal-to-noise ratio ~30 dB. Linear densities in excess of 1050 kbpi were achieved with thermal fly-height control, compatible with recording areal densities of ~400 Gb/in2. Current-induced spin-torque effects in the recording head were observed to result in rapid performance degradation above a threshold bias voltage of about 75 mV, corresponding to current densities >108 A/cm2.

Study of longitudinal stabilization using in-stack biasing

The in-stack stabilization of unshielded and shielded magnetic tunnel junction (MTJ) sensors have been studied experimentally by quasi-static and recording tests as well as theoretically by micromagnetic modeling. Results showed the viability of in-stack stabilization over a range of design and material conditions. Performance tradeoff studies and design optimization results led to the fabrication of MTJ read heads with good magnetic stability and high readback sensitivity.

Thin-Film Processing Realities for

Magnetic recording has maintained a cost/bit advantage over solid-state storage by using a single transducer to self-assemble bits with sub-lithographic dimensions on an unpatterned substrate. This paper explores the ability of magnetic recording to maintain this advantage at 1 Tbit/in2 by examining the process challenges associated with the fabrication of head structures at this areal density. Specifically, this paper describes the minimum feature, F, and alignment requirements for the thin-film head structures supporting 1 Tbit/in2 densities and compares these requirements with the projected roadmaps of the semiconductor industry. These comparisons indicate that minimum feature head processing requirements will match semiconductor capabilities in the time frame for 1 Tbit/in2 recording product. Further, alignment requirements for the head structure will exceed projected semiconductor capabilities in this same time frame. The process implications of the technologies of discrete tracks and patterned bits are analyzed, which move the minimum feature requirements from the head structure to the disk media. These approaches require patterning sub-lithographic bit cell dimensions which by definition exceed semiconductor lithographic capabilities.