Magneto-optical magnetic field polarity sensor

Claim 2

A memory device comprising a. a sheet of ferrimagnetic material capable of supporting magnetic domains, said sheet being divided into a plurality of small finite locations, each location being characterized by the presence of a magnetic domain having a fringing magnetic field associated therewith or by the absence of such domain, and b. a transparent magnetically uncompensated transducers layer comprising a bismuth-containing iron garnet having the formula Bi3 2xCa2xFe5 xVxO12 where 0.8 < x < 1.4, values of x resulting in a magnetically compensated crystal being excluded, said transducer layer being positioned on the surface of said sheet adjacent each of said finite locations respectively, the portions of said layer located adjacent said locations containing magnetic domains being within the fringing magnetic field associated therewith.

Claim 3

A magneto-optical device as defined by claim 1 wherein said transducer layer is divided into a plurality of individual transducers, each of said transducers being located adjacent one of the plurality of finite locations in said sheet of ferrimagnetic material characterized by the presence or absence of a magnetic domain.

Claim 4

Apparatus for sensing the polarity of a magnetic field comprising a. a transparent magnetically uncompensated transducer comprising a bismuth-containing iron garnet positioned within said magnetic field, said bismuth-containing iron garnet having the formula Bi3 2xCa2xFe5 xVxO12 where 0.8 < x < 1.4, values of x resulting in a magnetically compensated crystal being excluded, said transducer being characterized by an active cross-sectional area corresponding to that of the magnetic field whose polarity is to be sensed, a relatively large Faraday rotation, low coercive force and a demagnetizing field which is small in comparison with the magnetic field being sensed, b. means for generating a linearly polarized beam of electromagnetic energy having a cross-sectional area less than that of said magnetic field, said beam being transmitted through said transducer thereby having its axis of polarization rotated in a direction determined by the polarity of said magnetic field, and c. means optically coupled to said transducer for determining the direction of rotation of said beam of electromagnetic energy.

Claim 5

Apparatus for sensing the polarity of a magnetic field comprising a. a transparent magnetically uncompensated transducer comprising a bismuth-containing iron garnet positioned within said magnetic field, said bismuth-containing iron garnet having the formula Bi3 2xCa2xFe5 xVxO12 where 0.8 < x < 1.4, values of x resulting in a magnetically compensated crystal being excluded, said transducer being characterized by an active cross-sectional area corresponding to that of the magnetic field whose polarity is to be sensed, a relatively large Faraday rotation, low coercive force and a demagnetizing field which is small in comparison with the magnetic field being sensed, b. means for generating a linearly polarized beam of electromagnetic energy having a cross-sectional area less than that of said magnetic field, said beam being transmitted through said transducer thereby having its axis of polarization rotated in a direction determined by the polarity of said magnetic field, and c. means optically coupled to said transducer for determining the direction of rotation of said beam of electromagnetic energy.

Claim 6

Apparatus for sensing the presence of a magnetic domain having a fringing field at a given location within a sheet of ferrimagnetic material capable of supporting magnetic domains, said apparatus comprising a. a transparent magnetically uncompensated transducer comprising a bismuth-containing iron garnet positioned on the surface of said sheet at said given location within the fringing magnetic field of said domain, said bismuth-containing iron garnet having the formula Bi3 2xCa2xFe5 xVxO12 where 0.8 <x < 1.4, values of x resulting in a magnetically compensated crystal being excluded, b. means for generating a linearly polarized beam of light having a cross-sectional area less than that of said magnetic domain, said beam being transmitted through said transducer thereby having its axis of polarization rotated in a direction determined by the magnetization polarity of said domain, and c. means optically coupled to said transducer for determining the direction of rotation of the axis of polarization of said beam of light.

Claim 7

Apparatus for sensing the presence of a magnetic domain having a fringing field at a given location within a sheet of ferrimagnetic material capable of supporting magnetic domains, said apparatus comprising a. a transparent magnetically uncompensated transducer comprising a bismuth-containing iron garnet positioned on the surface of said sheet at said given location within the fringing magnetic field of said domain, said bismuth-containing iron garnet having the formula Bi3 2xCa2xFe5 xVxO12 where 0.8 <x < 1.4, values of x resulting in a magnetically compensated crystal being excluded, b. means for generating a linearly polarized beam of light having a cross-sectional area less than that of said magnetic domain, said beam being transmitted through said transducer thereby having its axis of polarization rotated in a direction determined by the magnetization polarity of said domain, and c. means optically coupled to said transducer for determining the direction of rotation of the axis of polarization of said beam of light.

Claim 8

Apparatus as defined by claim 4 wherein said means for generating a linearly polarized beam of light comprises a laser and plane polarizing means positioned in the path of the beam emitted by said laser.

Claim 9

Apparatus as defined by claim 4 wherein said means for determining the direction of rotation of the axis of polarization of said beam comprises an elliptical polarization analyzer and a photodetector, the amount of light reaching said photodetector being determined by the angular orientation of said elliptical polarization analyzer.

Claim 10

A magneto-optical device comprising a. a sheet of ferrimagnetic material capable of supporting magnetic domains, said sheet being divided into a plurality of small finite locations, said sheet of ferrimagnetic material comprising TbFeO3, each location being characterized by the presence of a magnetic domain having a fringing magnetic field associated therewith or by the absence of such domain, b. a transparent magnetically uncompensated transducer layer positioned on the surface of said sheet adjacent each of said finite locations respectively, said transducer layer comprising bismuth-containing iron garnet having the formula Bi3 2xCa2xFe5 xVxO12 where 0.8 < x < 1.4, values of x resulting in a magnetically compensated crystal being excluded, the portions of said layer located adjacent said locations containing magnetic domains being within the fringing magnetic field associated therewith, c. means for generating a linearly polarized beam of light having a cross-sectional area less than that of said finite location and directing said beam to a selected area of said transducer layer, the axis of polarization of said beam being rotated as it passes through said transducer area in a direction determined by the presence or absence of a magnetic domain adjacent said selected transducer area, and d. means optically coupled to said transducer layer for determining the direction of rotation of the axis of polarization of said beam of light.

Claim 11

A magneto-optical device comprising a. a sheet of ferrimagnetic material capable of supporting magnetic domains, said sheet being divided into a plurality of small finite locations, said sheet of ferrimagnetic material comprising TbFeO3, each location being characterized by the presence of a magnetic domain having a fringing magnetic field associated therewith or by the absence of such domain, b. a transparent magnetically uncompensated transducer layer positioned on the surface of said sheet adjacent each of said finite locations respectively, said transducer layer comprising bismuth-containing iron garnet having the formula Bi3 2xCa2xFe5 xVxO12 where 0.8 < x < 1.4, values of x resulting in a magnetically compensated crystal being excluded, the portions of said layer located adjacent said locations containing magnetic domains being within the fringing magnetic field associated therewith, c. means for generating a linearly polarized beam of light having a cross-sectional area less than that of said finite location and directing said beam to a selected area of said transducer layer, the axis of polarization of said beam being rotated as it passes through said transducer area in a direction determined by the presence or absence of a magnetic domain adjacent said selected transducer area, and d. means optically coupled to said transducer layer for determining the direction of rotation of the axis of polarization of said beam of light.

Claim 12

A magneto-optical device as defined by claim 7 wherein said transducer layer is divided into a plurality of individual transducers, each of said transducers being located adjacent one of the plurality of finite locations in said sheet of ferrimagnetic material characterized by the presence or absence of a magnetic domain.