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Physics and Design of Hard Disk Drive Magnetic Recording Read Heads

  • Stefan Maat
  • Arley C. Marley

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.

Keywords

Tunnel Junction Areal Density Tunnel Barrier Heusler Alloy Free Layer 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of 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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Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  1. 1.Magnetic Recording Heads DevelopmentHGST, a Western Digital CompanySan JoseUSA
  2. 2.HGST, a Western Digital CompanySan JoseUSA

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