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Transducer for Enhancing Longitudinal Magneto Optic Kerr Effect

IP.com Disclosure Number: IPCOM000074954D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Grimm, MA: AUTHOR

Abstract

Shown is a prismatic magneto-optic transducer for converting magnetization from tape 10 into variations in reflected light beam 12. Polarized light 14, incident upon prism 16, is passed to the thin films coated on the face of the prism and reflected from the thin films out of the prism. The Kerr magneto-optic effect takes place at the point of reflection on the thin films. The thin films in particular are made up of permalloy magnetic thin film 18 and dielectric film 20.

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Transducer for Enhancing Longitudinal Magneto Optic Kerr Effect

Shown is a prismatic magneto-optic transducer for converting magnetization from tape 10 into variations in reflected light beam 12. Polarized light 14, incident upon prism 16, is passed to the thin films coated on the face of the prism and reflected from the thin films out of the prism. The Kerr magneto-optic effect takes place at the point of reflection on the thin films. The thin films in particular are made up of permalloy magnetic thin film 18 and dielectric film 20.

The object of this transducer structure is to increase the figure of merit of the transducer. The figure of merit is defined as:
F = DeltaI over I(o) = R(P) Theta(p) - R(s)theta(s)

WHERE: R(P) and R(s) = Reflection Coefficients and theta(p) and theta(s) = Kerr Rotations

for (p) and (s) polarized light, respectively.

Dielectric film 20 is deposited on the magnetic thin film 18. The function of the dielectric film is to reduce the reflection coefficient R(s) to a minimum. With R(s) reduced to a minimum, the figure of merit is increased to a maximum.

In particular, R(s) is reduced by using dielectric thin films having a high refractive index, such as zinc sulfide, cerium dioxide, or titanium dioxide. For permalloy, NiFe, where N = 1.5 - j 2.3, d/lambda = 0.03, Q = 0.01e/j 45 degrees/, and a thickness of dielectric film d/lambda = 0.06 (lambda = wavelength of light), the figure of merit is increased by a factor of 5, as compared to the un...