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New Rotating Field Methods to Measure the Easy Axis Orientation And Anisotropy Field of Thin Ferromagnetic Films

IP.com Disclosure Number: IPCOM000101666D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 92K

Publishing Venue

IBM

Related People

Best, JS: AUTHOR [+5]

Abstract

In this article, two novel methods that permit the measurement and spatial mapping of the Easy Axis Orientation (EAO) and anisotropy field (Hk) for anisotropic, ferromagnetic films are disclosed. Although these techniques can be adapted to a variety of magnetometers, their full utility is achieved when a magneto-optic Kerr magnetization sensing system is used since such a sensor permits spatial mapping of EAO and Hk.

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New Rotating Field Methods to Measure the Easy Axis Orientation And Anisotropy Field of Thin Ferromagnetic Films

       In this article, two novel methods that permit the
measurement and spatial mapping of the Easy Axis Orientation (EAO)
and anisotropy field (Hk) for anisotropic, ferromagnetic films are
disclosed.  Although these techniques can be adapted to a variety of
magnetometers, their full utility is achieved when a magneto-optic
Kerr magnetization sensing system is used since such a sensor permits
spatial mapping of EAO and Hk.

      Critical Switching Curve Measurements (CSCM)

      When an applied magnetic field of constant magnitude H, which
is less than that of the anisotropy field, is rotated
counterclockwise in the plane of an anisotropic, ferromagnetic film,
the magnetization M of the film will tend to follow the applied field
direction. However, the angle of M will lag increasingly further
behind that of H until the total magnetic energy becomes sufficiently
high to allow another magnetic state of the film to be energetically
more favorable.  At this point, the magnetization undergoes a large
discontinuous change in direction which can be sensed by the
magneto-optic Kerr effect, a magnetoresistance change, or a pick-up
coil.  A simple graphical picture of the film energy is given by the
Stoner-Wohlfarth asteroid shown in the figure where the rotating
applied field is represented by the vector H which traces out a
circle, and the magnetization switches occur at the points where the
circle intersects the asteroid, which is also known as the critical
switching curve.  Thus, if the applied field begins its rotation from
a direction toward the right, the first switch is observed when H
reaches point A in the figure.  After continued counterclockwise
field rotation, the tip of the applied field vector again contacts
the asteroid at point B, resulting in another switch in magnetization
angle.  If the direction of applied field rotation is now reversed to
clockwise, behavior similar to that of the counterclockwise case will
result except that the...