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Physics and Design of Hard Disk Drive Magnetic Recording Read Heads

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Handbook of Spintronics

Abstract

Magnetic recording heads always have been on the forefront of technology. A finished magnetic recording head that is manufactured in high volume is the outcome of a coordinated effort of various scientific and engineering disciplines. This chapter will focus on the physics and design of modern magnetic recording read heads. It will explain the underlying concepts of thin film magnetism and electron transport in nanostructures and describe the aspects of device scaling, magnetic stabilization, signal-to-noise considerations, and read-back performance of currently employed tunnel magnetoresistive read heads. An outlook on possible future read-head technologies such as current-perpendicular-to-the-plane giant magnetoresistance, scissor, two-dimensional magnetic recording, and spin-torque sensors will be given.

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Abbreviations

α:

Magnetic damping constant

β:

Bulk spin-scattering parameter

γ:

Interface spin-scattering parameter

Θ:

Angle of layer magnetization with respect to the magnetic field

a:

Media transition length

ABS:

Air-bearing surface

ACL:

Antiferromagnetic coupling layer

AF:

Antiferromagnet

AMR:

Anisotropic magnetoresistance

bcc:

Body-centered cubic

BP:

Bias point

CFAS:

Co2Fe0.5Al0.5Si

CIP:

Current in plane

CL:

Cap layer

CMP:

Chemical mechanical polishing

CPP:

Current perpendicular to the plane

FL:

Free layer

g:

Gyromagnetic ratio

GBit/in2 :

Gigabit/square inch

GMR:

Giant magnetoresistance

H:

Magnetic field

H⊥ :

Magnetic out-of-plane stiffness field

hcp:

Hexagonal close packed

HD :

Demagnetization field

HHB :

Hard-bias field

HII :

Magnetic in-plane stiffness field

HMS:

Head-media spacing

IBD:

Ion beam deposition

IBM:

International Business Machines

kB :

Boltzmann constant

lSF :

Spin-diffusion length

MF :

Free layer magnetization

MR:

Magnetoresistance

Mr :

Remanent magnetization

MRW:

Magnetic read width

Ms :

Saturation magnetization

OTC:

Offtrack capability

OTP:

Offtrack position

P:

Spin polarization

PL:

Pinned layer

PVD:

Physical vapor deposition

PW:

Pulse width

R:

Resistance

R0 :

Sensor resistance at zero field

RA:

Resistance-area product

RAC :

Alternating current resistance

RAP :

Sensor resistance in the antiparallel state

RDC :

Direct current resistance

RG:

Read gap

RHmax :

Sensor resistance for negative media field

RHmin :

Sensor resistance for positive media field

RKKY:

Ruderman-Kittel-Kasuya-Yosida

RL:

Reference layer

RP :

Sensor resistance in the parallel state

S:

Noise spectral density

S1:

Bottom shield

S2:

Top shield

SH:

Stripe height

SL:

Seed layer

SNR:

Signal-to-noise ratio

SQTP:

Squeeze track pitch

SSS:

Shield-to-shield spacing

T:

Absolute temperature in Kelvin

t:

Thickness

TB:

Tunnel barrier

TDMR:

Two-dimensional magnetic recording

TFC:

Thermal flight-height control

TMR:

Tunnel magnetoresistance

TW:

Track width

u:

Utilization

Vb :

Bias voltage

VF :

Free layer volume

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Authors and Affiliations

  1. Magnetic Recording Heads Development, HGST, a Western Digital Company, 5601 Great Oaks Parkway, San Jose, CA, 95119, USA

    Stefan Maat

  2. HGST, a Western Digital Company, San Jose, CA, USA

    Arley C. Marley

Authors
  1. Stefan Maat
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  2. Arley C. Marley
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Correspondence to Stefan Maat .

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Editors and Affiliations

  1. York-Nanjing International Center of Spintronics, Nanjing University, Nanjing, China

    Yongbing Xu

  2. Institute for Molecular Engineering, University of Chicago, Chicago, Illinois, USA

    David D. Awschalom

  3. Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai, Japan

    Junsaku Nitta

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Maat, S., Marley, A.C. (2016). Physics and Design of Hard Disk Drive Magnetic Recording Read Heads. In: Xu, Y., Awschalom, D., Nitta, J. (eds) Handbook of Spintronics. Springer, Dordrecht. https://doi.org/10.1007/978-94-007-6892-5_35

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