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Method to Measure the Magnetic Coupling Between Magnetic Layers

IP.com Disclosure Number: IPCOM000105096D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Chang, JW: AUTHOR [+5]

Abstract

Disclosed is a method to evaluate the quality of the exchange coupling at the interface between magnetic thin films. A surface average of the interface coupling is estimated from the response of the magnetization under the influence of internal currents and external fields: a rotation (fanning) of the magnetization as a function of depth in the films. The fanning angle can be measured electrically by changes in the magnetoresistance of the films.

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Method to Measure the Magnetic Coupling Between Magnetic Layers

      Disclosed is a method to evaluate the quality of the exchange
coupling at the interface between magnetic thin films.  A surface
average of the interface coupling is estimated from the response of
the magnetization under the influence of internal currents and
external fields: a rotation (fanning) of the magnetization as a
function of depth in the films.  The fanning angle can be measured
electrically by changes in the magnetoresistance of the films.

      Consider a magnetic thin film sample patterned in the form of a
stripe with the easy-axis along the length of the stripe.  If current
flows uniformly through the stripe, it will generate an internal
magnetic field with a linear profile through the depth of the stripe
(Fig. 1).  Under the influence of the internal field, the
magnetization in the stripe will then rotate (fan out) by an angle
&theta which varies through the thickness of the film [*].

      There are two different regimes depending on the stripe
thickness.  For thin film, exchange coupling constrains the amplitude
of fanning.  The rate of rotation at the center of the film is
proportional to J Ms T sup 2 / A, where J is the current density, Ms
the saturation magnetization, T the film thickness and A the exchange
constant [*].  For thicker films, the fanning is dominated by
anisotropy: the magnetization is balanced between the internal field
and the anisotropy field H sub k. The rate of rotation at the center
is proportional to J/ H sub k.

      Consider now a thin film consisting of two magnetic layers with
thickness's T/2, that is patterned in the form of a wide stripe.
Changes in magnetoresistance can then be measured for different
current densities as a function...