Magneto-optical processes and elements using tetrahedrally coordinated divalent cobalt-containing magnetic material

Claim 2

A MAGNETO-OPTICAL READOUT PROCESS WHEREIN ELECTROMAGNETIC RADIATION IS USED TO DETERMINE THE DIRECTION OF MAGNETIZATION WITHIN DISCRETE AREAS OF A MAGNETIC ELEMENT, SAID PROCESS COMPRISING: A. PROVIDING A MAGNETIC ELEMENT HAVING DISCRETE AREAS WHICH ARE MAGNETIZED, EACH OF SAID AREAS COMPRISING AN INORGANIC CRYSTALLINE MATERIAL HAVING A MAGNETICALLY ORDERED CRYSTAL SUBLATTICE CONTAINING TETRAHEDRALLY COORDINATED DIVALENT COBALT IN AN AMOUNT SUFFICIENT TO PROVIDE A KERR ELLIPTICITY GREATER THAN 0.25*,

Claim 3

A magneto-optical readout process as defined in claim 1 wherein said radiation has a wavelength within the range of from about 0.5 to about 2.5 microns.

Claim 4

A magneto-optical readout process as defined in claim 1 wherein said crystalline material comprises divalent cobalt in at least 10 percent of said tetrahedral sublattice sites.

Claim 5

A magneto-optical readout process as defined in claim 1 wherein said radiation is polarized and has a wavelength within the range of about 0.5 to about 2.5 microns.

Claim 6

A magneto-optical readout process wherein electromagnetic radiation is used to determine the direction of magnetization within discrete areas of magnetic element, said process comprising: a. providing a magnetic element having discrete areas which are magnetized, each of said areas comprising an inorganic crystalline material having a magnetically ordered crystal sublattice containing tetrahedrally coordinated divalent cobalt in an amount sufficient to provide a Kerr ellipticity greater than 0.25*, b. exposing at least one of said discrete areas to electromagnetic radiation having a wavelength within the range of from about 0.5 to about 2.5 microns, and c. detecting the change in polarization of said radiation caused by said cobalt to determine the direction of magnetization within said discrete area which has been exposed.

Claim 7

A magneto-optical readout process wherein electromagnetic radiation is used to determine the direction of magnetization within discrete areas of magnetic element, said process comprising: a. providing a magnetic element having discrete areas which are magnetized, each of said areas comprising an inorganic crystalline material having a magnetically ordered crystal sublattice containing tetrahedrally coordinated divalent cobalt in an amount sufficient to provide a Kerr ellipticity greater than 0.25*, b. exposing at least one of said discrete areas to electromagnetic radiation having a wavelength within the range of from about 0.5 to about 2.5 microns, and c. detecting the change in polarization of said radiation caused by said cobalt to determine the direction of magnetization within said discrete area which has been exposed.

Claim 8

A magneto-optical readout process wherein electromagnetic radiation is used to determine the direction of magnetization within discrete areas of a magnetic element, said process comprising: a. providing a magnetic element having discrete areas which are magnetized, each of said areas comprising an inorganic magnetic chalcogenide spinel having the following formula:

Claim 9

A magneto-optical readout process wherein electromagnetic radiation is used to determine the direction of magnetization within discrete areas of a magnetic element, said process comprising: a. providing a magnetic element having discrete areas which are magnetized, each of said areas comprising an inorganic magnetic chalcogenide spinel having the following formula:

Claim 10

A process as defined in claim 6 wherein said radiation is polarized and has a wavelength within the range of from about 0.5 to about 2.5 microns.

Claim 11

A process as defined in claim 6 wherein 0.10 < or = x < or = 1.0.

Claim 12

A process as defined in claim 6 wherein said spinel has a Curie temperature greater than about 200*K.

Claim 13

A process as defined in claim 6 wherein said spinel has a Curie temperature greater than about 298*K and less than about 600*K.

Claim 14

A process as defined in claim 6 wherein said spinel is selected from the group consisting of Fe0.75Co0.25CrS4, Fe0.5Co0.5CrS4, CoCr2S4, and CoFeRhS4.

Claim 15

A process as defined in claim 6 wherein said magnetic material comprises a hot-pressed magnetic chalcogenide spinel.

Claim 16

A process as defined in claim 6 wherein the change in polarization of said radiation is detected using a reflectance mode of optical readout.

Claim 17

A process as defined in claim 6 wherein the change in polarization of said radiation is detected using a transmission mode of optical readout.

Claim 18

A magneto-optical readout process wherein electromagnetic radiation is used to determine the direction of magnetization within discrete areas of a magnetic element, said process comprising: a. providing a magnetic element having discrete areas which are magnetized, each of said areas comprising an inorganic magnetic chalcogenide spinel having the following formula:

Claim 19

A magneto-optical readout process wherein electromagnetic radiation is used to determine the direction of magnetization within discrete areas of a magnetic element, said process comprising: a. providing a magnetic element having discrete areas which are magnetized, each of said areas comprising an inorganic magnetic chalcogenide spinel having the following formula:

Claim 20

In a thermomagnetic recording process for the storage and retrieval of information wherein a. a magnetic field is applied to an element comprising a magnetic inorganic crystalline material magnetized in a direction different from that of said field, said field being of insufficient strength to alter the magnetization of said material at a temperature below the Curie temperature of said material, said field applied while at least one selected area of said material is raised to a temperature above the Curie temperature of said material to change the direction of magnetization in said selected area, b. the temperature of said selected area is lowered below the Curie temperature of said material, c. the element is exposed to electromagnetic radiation, and d. the change in polarization of said radiation caused by the change in the direction of magnetization in said selected area is detected, the improvement wherein: a. said material has a crystal sublattice which contains magnetically ordered tetrahedrally coordinated divalent cobalt in an amount sufficient to provide a Kerr ellipticity greater than 0.25*, and b. said radiation to which said element is exposed corresponds to a crystal field transition of said divalent cobalt.

Claim 21

In a thermomagnetic recording process for the storage and retrieval of information wherein a. a magnetic field is applied to an element comprising a magnetic inorganic crystalline material magnetized in a direction different from that of said field, said field being of insufficient strength to alter the magnetization of said material at a temperature below the Curie temperature of said material, said field applied while at least one selected area of said material is raised to a temperature above the Curie temperature of said material to change the direction of magnetization in said selected area, b. the temperature of said selected area is lowered below the Curie temperature of said material, c. the element is exposed to electromagnetic radiation, and d. the change in polarization of said radiation caused by the change in the direction of magnetization in said selected area is detected, the improvement wherein: a. said material has a crystal sublattice which contains magnetically ordered tetrahedrally coordinated divalent cobalt in an amount sufficient to provide a Kerr ellipticity greater than 0.25*, and b. said radiation to which said element is exposed corresponds to a crystal field transition of said divalent cobalt.

Claim 22

In a magnetic transducer for use in a magnetic playback head which employs a magneto-optical readout, said transducer containing a thin layer of an inorganic crystalline magnetic material, the improvement wherein said magnetic material has a crystal sublattice which contains magnetically ordered tetrahedrally coordinated divalent cobalt in an amount sufficient to provide, at a temperature greater than about 298*K and at a wavelength corresponding to a crystal field transition of said cobalt, a Kerr ellipticity greater than 0.25*.

Claim 23

In a magnetic transducer for use in a magnetic playback head which employs a magneto-optical readout, said transducer containing a thin layer of an inorganic crystalline magnetic material, the improvement wherein said magnetic material has a crystal sublattice which contains magnetically ordered tetrahedrally coordinated divalent cobalt in an amount sufficient to provide, at a temperature greater than about 298*K and at a wavelength corresponding to a crystal field transition of said cobalt, a Kerr ellipticity greater than 0.25*.

Claim 24

A magnetic transducer as defined in claim 17 wherein said Kerr ellipticity is obtained at a wavelength within the range of from about 0.5 to about 2.5 microns.

Claim 25

In a magnetic recording element comprising a support bearing a layer of an inorganic magnetic crystalline material, said element adapted for use in a magneto-optical readout process, the improvement wherein said magnetic crystalline material has a crystal sublattice which contains magnetically ordered tetrahedrally coordinated divalent cobalt in an amount sufficient to provide, at a wavelength corresponding to a crystal field transition of said cobalt, a Kerr ellipticity greater than 0.25*.

Claim 26

In a magnetic recording element comprising a support bearing a layer of an inorganic magnetic crystalline material, said element adapted for use in a magneto-optical readout process, the improvement wherein said magnetic crystalline material has a crystal sublattice which contains magnetically ordered tetrahedrally coordinated divalent cobalt in an amount sufficient to provide, at a wavelength corresponding to a crystal field transition of said cobalt, a Kerr ellipticity greater than 0.25*.

Claim 27

A magnetic recording element as defined in claim 19 wherein said Kerr ellipticity effect is obtained at a wavelength within the range of from about 0.5 to about 2.5 microns.

Claim 28

A magnetic recording element comprising a support bearing a thin layer of an inorganic magnetic crystalline material, said magnetic crystalline material having an electrical resistivity greater than about 104 ohm-cm., a coercivity greater than about 500 oersteds, and a remenence of its magneto-optical effect greater than about two-thirds the saturation value; said magnetic crystalline material having a crystal sublattice which contains magnetically ordered tetrahedrally coordinated divalent cobalt in an amount sufficient to provide, at a wavelength corresponding to a crystal field transition of said cobalt, a Kerr ellipticity greater than 0.25*; said magnetic crystalline material having the following formula:

Claim 29

A magnetic recording element comprising a support bearing a thin layer of an inorganic magnetic crystalline material, said magnetic crystalline material having an electrical resistivity greater than about 104 ohm-cm., a coercivity greater than about 500 oersteds, and a remenence of its magneto-optical effect greater than about two-thirds the saturation value; said magnetic crystalline material having a crystal sublattice which contains magnetically ordered tetrahedrally coordinated divalent cobalt in an amount sufficient to provide, at a wavelength corresponding to a crystal field transition of said cobalt, a Kerr ellipticity greater than 0.25*; said magnetic crystalline material having the following formula:

Claim 30

A magnetic recording element comprising a support bearing a thin layer of an inorganic magnetic crystalline material, said element adapted for use in a magneto-optical readout process, said magnetic crystalline material having a crystal sublattice which contains magnetically ordered tetrahedrally coordinated divalent cobalt in an amount sufficient to provide, at a wavelength corresponding to a crystal field transition of said cobalt, a Kerr ellipticity greater than 0.25*; said magnetic crystalline material having the following formula:

Claim 31

A magnetic recording element comprising a support bearing a thin layer of an inorganic magnetic crystalline material, said element adapted for use in a magneto-optical readout process, said magnetic crystalline material having a crystal sublattice which contains magnetically ordered tetrahedrally coordinated divalent cobalt in an amount sufficient to provide, at a wavelength corresponding to a crystal field transition of said cobalt, a Kerr ellipticity greater than 0.25*; said magnetic crystalline material having the following formula:

Claim 32

A magnetic recording element as defined in claim 22 wherein said magnetic crystalline material is selected from the group consisting of: Fe0.75Co0.25Cr2S4 , CoFeRhO4 , Fe0.5Co0.5Cr2S4 , and CoCr2S4 .

Claim 33

A magnetic recording element as defined in claim 22 wherin said magnetic crystalline material is CoCr2S4 or CoCr2O4.