Browse Prior Art Database

Method to Measure the Magnetic Anisotropy in Small Magnetic Structures

IP.com Disclosure Number: IPCOM000117210D
Original Publication Date: 1996-Jan-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 118K

Publishing Venue

IBM

Related People

Chang, JW: AUTHOR [+5]

Abstract

Figure 1. (a) Fanning of the magnetization under the influence of a current in the stripe. Solid arrow: magnetization at the top surface; dashed arrow: magnetization at the bottom surface. (b) Cross sectional view AA' of the stripe, showing the fanning of the magnetization through the thickness; the magnetic poles (+ and -) at the edges of the stripe; and the demagnetizing field, H sub d, which is localized at the edges of the stripe and small compared to that induced by uniform magnetization along the width of the stripe.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Method to Measure the Magnetic Anisotropy in Small Magnetic Structures

Figure 1.
  (a) Fanning of the magnetization under the influence of a current
in
       the stripe.  Solid arrow: magnetization at the top surface;
dashed
       arrow: magnetization at the bottom surface.
  (b) Cross sectional view AA' of the stripe, showing the fanning of
       the magnetization through the thickness; the magnetic poles
       (+ and -) at the edges of the stripe; and the demagnetizing
       field, H sub d, which is localized at the edges of the stripe
       and small compared to that induced by uniform magnetization
       along the width of the stripe.

Figure 2.
  Electrical circuits for a magnetoresistive evaluation of a thin
film
   head magnetic circuit.

      More complete characterization of magnetic materials at the
wafer and row level can improve product yields and reduce costs in
magnetic thin film head manufacturing.  This also applies to any
product in which the manufacturing quality of small magnetic
structures needs to be evaluated.

      Disclosed here are methods to measure the magnetic anisotropy
in small structures, such as stripes or thin-film recording heads.
The magnetic anisotropy is estimated from the magnetoresistive
response of the magnetization under the combined influence of
internal currents and external fields.  Magnetostriction can be
deduced from stress-induced changes in the total anisotropy.

      These characterization methods are superior to alternate
techniques such as BH looper measurements, which are difficult to
apply to small complex magnetic structures and magneto-optic
techniques which only probe the surface of magnetic materials.  The
methods presented here can be implemented with test sites on a wafer
(part A), or in partially completed heads (part B) with no additional
manufacturing steps.

A) Test sites.

      It is relatively straightforward to obtain a comparative
evaluation of test sites using magnetoresistance.  However, to obtain
more quantitative information it is necessary to controllably change
the magnetization state of the structure under study.  In very thin
layers (e.g., less than a few tenths of micrometers thick for present
day structures), in-plane demagnetizing factors are small.  The
anisotropy field, H sub k, can be obtained directly from changes in
the resistance under the influence of saturating external fields.
For thicker materials, demagnetizing factors are not small and very
large applied fields are needed for saturation (typically thousands
of Oersteds); this may be impractical.  The method proposed here uses
a combination of internal currents and small external fields instead
of large external fields alone to change the magnetization state.

   ...