CA2248602A1 - Compositions comprising cystalline-like transition metal material and methods of use thereof - Google Patents

Abstract

The invention encompasses applications including, but not limited to, (1) lightweight ferromagnetic applications, computer and data storage technology;
(2) recording technology; (3) photocopying devices; (4) optical switches; (5) magnetic analog film and (6) electronic devices and sensors.

Description

COMPOSITIONS COMPRISING CYSTALLIN~-LIKE TRANSITION METAL
MATERIAL AND METHODS OF USE THEREOF

CROSS-REFFRFNCE TO ~<FT ~TFr) APPT TCATIONS
This application is a continn~tion-in-part of U.S. application Serial No. 08/621,363 filed March 25, 1996, which is a continu~tion-in-part of U.S. Application Serial No.
08/228,782, filed April 18, 1994 and issued as U.S. Patent No. 5,501,808.

FTFT n OF THF INVF~TION
This invention relates to materials having a crystalline-like structure which comprise transition metals that exhibit unique electronic properties.

psACKGROUNn OF THF I~VF.I~TION
Photom~nPtic compounds have been known for some time, they are also referred to as m~gn~to-optical (MO) materials. Enz et al. (1970) Philips Tech. Rev. 31 :33, Enz et al. (1971) J. Phys. (Paris) Colloq: Pt. 2 1-703; and Verdaguer (1996) Science 272:698.
The changes in magnetic properties that generally occur are either an increase or decrease in intrinsic m~gn~ti7~tion, where the compounds can exist in a ferrom~gn~tic, par~m~n~?tic or ~ m~gnetic state.
Beginning in the late 1980's, MO materials were utilized in devices that store and retrieve m~gnetic information. The m~teri~l~ are considered to be magneto-optical but in reality use thermal heating supplied by a laser to affect the m~gn~tic properties of the material. The principle is to raise the surface to a len~ dl~e above the Curie point where the m~gnetic domains can be easily aligned ~,vith an applied magnetic field. Kryder (1993) Annu. ~ev. Ma~er. Sci. 23:411. The information stored in the magnetically aligned domains is retrieved by a second polarized low power laser that is altered by an effect known as the polar Kerr rotation. The polarization angle of the light is rotated when reflected from the magnetically polarized surface. A drawback of this type of MO system ..
is that the effective area in which information can be stored, known as the areal density is much larger than the width of the laser beam due to thermal plopdg~lion into the medium.

., . . . ., . = .. ........ ..

W 0 97136294 PCT~USg7/05401 Also, the speed at which the m~n.o.tic l,~ol)tlLy can be altered is limited to the speed of sound in the material, which is generally~much slower than typical electronic excitations.
MO disk drives are a growing technology that are fmding their way into conl~u as a form of high capacity erasable storage. When they were introduced into the marketplace in 1989, a removable 5" disk had a storage capacity of 650 megabytes of information. MO disks are also extremely stable in a magnetic field. However, 5" disks "proved unwieldy for personal use." Kryder (1993). Despite this and other drawbacks of the MO disk, it enjoyed sales of an estim~tçcl $261 million in 1991 and was projected to grow at a 26% rate over the 6 subsequent years.
The MO drive has a few qualities that distinguish it from typical m~gnetiC storage.
The MO drive can be thought of as a cross b~lw~en a floppy disk drive and a fixed hard disk drive. The MO drive is like a floppy drive because its disk is removable and like a hard drive because large amounts of data can be stored. This combination provides for a cost-effective way of storing large amounts of data. For ~ lc, a 3" MO drive can hold 127 megabytes of data. A further advantage of the MO drive is that it is virtually impervious to the effects of a m~gn~.tic field at room t~ e~ . This is an effect that neither floppy disks nor fixed hard disks can offer. Briefly, this effect is due to the use of a thin film whose coercivity is strongly te~ el~l lre deptndP-nt In addition to all these benefits, the MO drive has enhanced stability. MO disk drives show promise of having at least a ten year life span on the media, and twenty years can be expected. Also, anisotropy can be expected to suffer no more than a 10% reduction in 70 years of ~nn~ling at 50~C.
All of these l~lu~ lies (high storage capacity, una~e~iled by a m~gn~tic field and long-term stability) made the MO disk an appealing new technology.
The MO drive also has some drawbacks that have prevented it from replacing conventional hard disk drives. The MO drives do not l.elro~lll as well as fixed hard disk drives. They have access times of 50 to 100 msec instead of the 10 to 15 msec for hard disk drives. MO drives also have data rates of about 1 megabyte per second instead of the 2 or 3 megabytes per second that hard disk drives have. These drawbacks along with the fact that MO drives are still rare have made it difficult for MO drives to gain widespread acceptance and popularity.
Given the advantages and disadvantages of the MO disk drive as explained above, the MO disk cannot replace either the floppy disk or the hard disk. The MO drive is too expensive and too rare to be used in place of a floppy disk while too slow to be used in place of a hard disk. Even still, the MO disk has found its place in the field of data storage.
The MO drive is best suited for storage of data that is large or infrequently used. In this way, a set of data can be written to the MO disk and literally put on the shelf until it is needed again.
A thin film can be any film b~ el1 a few Angskoms and a few microns.
Deposition of thin films is a complicated science and in pr~rti~lity, more of an art. Most deposition processes require very high vacuum, ~ much as 10-10 Torr for some applications. There are a number of dif~ deposition methods available, depending on the application. For deposition of the rare earth - transition metal films used in MO drives, g has been found to work well.
Because of the strict vacuum re4ui,~nlc"l~ that thin films have, there is a great deal of sophistic~tion required from vacuum technologies. Not only must leaks be sealed, but the vacuum rh~mber must be clean so that c~ ni-~ n does not ev~olal~ offand get deposited on the film. Gas leakage ll~o~lgll the chamber wall as well ~ evaporation of the chamber wall must also be considered at higher vacuums.
Sl,uLI. ,h1g is a technique where a target is put under vacuum with a substrate and bombarded such that atoms from the target are ejected and deposited on the substrate. The target is bombarded with high energy particles (e.g., 1 keV Ar ions) that shake atoms off of the target and into the vacuum. Once in the vacuum, the atoms from the target deposit on the substrate, as well ~ the chamber walls. One major advantage to ~ul~ g is that it allows for the deposition of films having the same composition ~ the target. Other techniques do not n~cess~nly have this advantage because dirr~ ,~,ll atoms ~v~oldle at dir~,e,ll rates and diffusion rates are high at the high tell~ ld~ s used by other techniques. Hence, a target can be made with a specific composition and ~lJull~ed with the assurance that the right composition will be deposited on the ~ul.~ le The b~ic theory behind the MO drive is the use of a substance that h~ very te~ ~e sensitive m~netic ~ ,e,Lies. This ~ c must have a curie t~ lu e -~ well above room te,~ e,dlure. The curie t~lllpe~alulci is the tt;nlp~ where a m~teri~l changes between î-, .u---~gntotic and p~r~m~nPtic. Below the curie It;lllptl~llUle, the substance is ferrom~gnPtic and h~ a ..,~ klic ~usce~tibility of (~105), me~ning that it is very difficult to change the magnetic field ~sociated with the ~-bst~nce Above the curie te.llpel~Lulc, the snbst~n~e is par~m~gn~tiC and has a m~gn~tic susceptibility of (~10-6), m~ning that the m~gnçtic field of the s~l~st~nce will change easily according to the surrounding m~gn~tic field. This change from ferromagnetic to par~m~gnetiC is used by the MO drive to write and erase with the use of a laser and a m~gn~tic field.
Writing to an MO disk can be seen sçh~m~tic~lly in Figure 1 A. All of the domains are initially set in the "upward" direction. Hence, only the "downward" direction domains need to be written. The process begins with applying a m~gn~tic field to the disk in the downward direction. The field applied is significantly less than that needed to effect the film at room tc;l~ .d~u~e so the film remains unaffected. Then, a diode laser of micron size is pulsed onto the film's surface. In the areas where the laser is pulsed, the film is heated by about 300~C. This is enough to raise the lelllyelalule of the fi}m above the curie t~lllyc.alu~e where the film is easily altered. At this point, the m~gnçti7~tion of the lased domain changes to the downward direction, that is, the direction of the applied field.
When the pulse stops, the film cools and freezes in the dowllw~d m~ l ;on. A
downward domain may be used to l~lJles~,-ll a 1 in binary nlC-llul~, while the upward domains may be used to rGyles~ a 0. In practice, two domains are needed for each bit.
The second domain is always a 0 and is used for comydlison so that the 1 will berecognized without ambiguity.
Ovelwl;~ g inform~tirn in the MO drives available today is done by a two step process. First, the old information is erased. This is done by setting the m~gnçtic filed in the upward direction and running the laser continuously as the disk is rotated. Then, the m~gnPtic field is set to the downward direction and the new information is written, as before, by pulsing the laser. Thus, two passes are r~luh~d to overwrite h~lllldlion. This inherent inefficiency slows the MO drive and is a major Ldwl,acl~ of the MO drive.
However, single-pass overwriting would require that the m~gn~tic field be modulated at the data rate. Furthermore, the m~gnPtic head would have to be small and very close to the recordi~g film so that the domains that are cooling would not be affected. This would el i ~ e a major advantage of the MO drive, its large head-to-media sp?lcing -~ Reading the m~gn~tQ-OptiC media also uses the laser in the drive, but at a reduced hl~e~si~y so that no significant heating takes place. The magnetic field could be read with a m~gn~tic head, but that would require a very small head that is very close to the media. As mentioned above, such a setup would elimin~te a key advantage of the MO drive. Figure l B shows a sc.hPm~tic of how data are read off a m~gneto-optical disk. The diode laser emits a reduced beam that passes through a polarizer and is focused onto the disk.
According to the polar Kerr MO effect, the plane of depolarization is rotated a small angle - I (K), depending on the m~nPti7~tion of the domain reflecting the beam. The reflected light is then split by a beam splitter and sent through a second plane polarizer called the analyzer. The analyzer can then be positioned such that the beam reflected by an upward magnetization is canceled out completely. This could register a 0 when no signal is detected by the photodetecter. The beam reflected from a downward m~gneti7~tion would then pass through the analyzer, at least in part, and be detected by the photodetecter. This could then register a 1. Thus, the binary pattern on the MO disk is read using the polar Kerr m~gneto-optic effect.
In an effort to fit more data on a disk, short wavelength media is being invçstig~tlo(t It is a relatively simple task to develop a laser that emits at 400 nm for use in place of the 800 nm standard. The difficulty comes in finding a material that will hold the npcess~ry m~gnçtic field in such a small riom~in The most promising materials under investi~tiQn are g~rnPt~, although there are still problems to be resolved.
Garnets have many attractive plop~llies that make them appear promising for future MO applications. While their MO effects are small near the 800 nm range, the effects become large around 400 nm. Garnets are also very stable against corrosion and long-term Pnn~lin~ They are even resistant to ~nn~ling at l~ e.dlu~s of several hundred degrees centigrade. These prop~llies make the garnets a very attractive choice for short wavelength media.
Unfortunately, there are two major problems with garnets that are not yet resolved.
Since gamets are so resistant to ~nnto~ling at high t~ es~ the substrates must also be as durable because the garnets must be deposited at even higher te~ .,ldlu~es. This rules out the plastic substrates used for the current MO disks. Most sllbsl,~es are too expensive for a low cost storage media, except for one: glass. Because of its low cost and high durability with respect to ~ ?~,ldlure and corrosion, glass may very well be the only -- substrate that garnets can use, at least for the time being. The other major problem with garnets is that they have a poor signal-to-noise ratio. Garnets tend to have grain sizes of around 400 nm which causes domain walls to follow the grain boundaries. This causes large fluctll~tions in domain size and a large amount of noise. Some work in~lic~tçs that W O 97/36294 PCTnUS97/05401 grain sizes have been made as low- as 3Q nm. This would in(iic~te that the problem of domain walls following grain boundaries may soon be solved.
A recent conclusion is that MO disk drives are a growing technology that are finding their place in the mass storage arena. Because of their large storage capacities and S relatively slow read/write times, they are best suited for large amounts of data that are not used very frequently. There is a lot of technology involved in the deposition of thin filrns, but there is still quite a bit to be learned in that area as well. The MO drive works on the basis of a large magnetic field turning a small domain when it is heated above its curie te,lllJe~ t; by a laser.
Ov~ ing old data requires two passes of the writing head, one to erase the data and another to write in the new data. This double pass is one of the reasons that MO drives are slower than more conventional m~n~tic hard disks. Reading data from a MO disk involves a plane polarized, low intensity laser beam that is rotated by the m~ el; ~ on of the domain being read (polar Kerr effect). It has been predicted that future MO drives win probably have garnets on a glass subal~dle using a laser with a wavelength of 400 nm.
Optical switches or optical switching is an illlpo. l~lt future goal of the co...l,u~.
industry. Islam (1993) Byte 17:183. The definition of an optical switch is a device that allows one light signal to affect a plop~lly of second light signal. There are several types of optical switches that have been developed most of which are electro-optical; these are switches that require an external electrical potential in order to function. McIntyre et al.
(1990) SPIE Proc. Ser. 1378:162. Recently, a few optical switches have been developed which require only light to operate and are the most desirable in the proposed optical computer industry. Unfortunately, these switches, which are based on light-in.luced c~mic~l or structural alterations in the switch m~t~ri~l, are by nature slow and so their usefulness is ~imit~cl Islam (1993); and Wood et al. (1989) SPIE Proc. Ser. 1105: 154.
Photocopying is generally accomplished by using a material that develops an electrostatic charge when irradiated with light. Mercer (1967) "Photography and Photocopying" 3rd ed. MacDonald and Evans, London, pp. 29-34. An electrostatic ink is -- then applied to the areas which have been exposed to light forrning an image. A drawback of this design is that most materials respond to electrostatic charge and this can lead to transfer of unwanted static charge to the other parts of the m~-~.hine. This can in turn affect the functioning of the photocopier. The use of photomagnetic materials in place of the . . ~ . ., W O 97/36294 PCTnUS97/05401 elec~lOs~lic compounds cullc~ y in use limits this problem since most materials do not respond to magnetic fields.
The development of new materials with intrinsic parameters which affect electronic pl~ope~ lies has become increasingly more i~n~uol~lt and has begun to enco,l.pass a variety of scientific disciplines. Covalent crystalline materials cont~ining delocalized pi systems are known to exhibit interesting electronic plo~clLies when combin~d with other characteristics such as partially filled electronic energy levels and certain types of ele.,lloll-phonon coupling. See, for example, Kittel, Introduction to Solid State Physics, 6th Ed., John Wiley & Sons, Inc., New York (1986), pp. 338-340. Examples of materials that have these plo~cllies are intercalated gld~hile and n-doped polyacetylenes described by Zhu et al., Nature, 355:712-714 (1992), p-doped polyaniline described by MacDiarmid et al., Synth. Met., 18:285 (1987), sulfur nitride (SN) described by Labes et al., Chem. Rev., 79:1 (1979), and intercalated C60 described by Haddon et al., Nature, 350:320-322 (1991).
These m~t~ri~lc can exhibit a range of p~ ~ from semiconductor to metallic-like conductivities and many are slll.e.co~ ting. For example, the intercalated C60 m~t~ri~l can have a supercon.lnctin~ conversion t~lllpeldlul., (Tc) as high as 45 K.
Some copper oxide col~ P coll~oullds have been found to have a Tc value as high as 125 K, which is believed to be due to planes of copper and oxygen that extend through these m~tçri~lc See Cava, Sci. Amer., 263:42~9 (1990). Copper and oxygenatoms positioned within a plane form only 90~ and 180~ angles for bonding. Such bonding may have an illll)oll~l~ impact on the electronic system since the d and p electron orbitals for the atoms are orthogonal to each other. The perfollllance of the copper oxide co~ ;..ing compounds has raised interest in investig~tin~ m~t~ri~lc with a structure and ~lim~ncionality similar to a copper-oxygen plane. ~tçri~lc which geometrically mimic a planar structure are Hofmann cl~ ales and the best known of these is Ni(CN)2NH3C6H6 disclosed by Iwamoto, Inclusion Compounds, 1:29-42, ~c~r~emic Press, London (1984).
However, the m~t~ri~l's electronic ~ o~.lies are not very interesting. It is a very good ine~ tor and has the predicted negative resistance versus ~ e.~ e slope for insulators.
There is no evidence of pi deloc~li7~tion over the crystal structure. It is believed the delo. ~li7~d pi system in these compounds is lirnited and extends only over the units of [Ni(CN)4]2-. Other compounds with structures which mimic a Cu-O plane are "Prussian Blues" described by Shriver et al., Inorg Chem., 4:725-730 (1965). These compounds WO 97/36294 PCT/US97/0~401 differ in the respect that the nc;lw~lk~ are three-flimPneional, coneieting of octahedral transition metals interlinked by linear cyanide units. These compounds are not claLhld~es and contain counter ions such as alkali metals in the lattice. Deloc~li7~tiQn in these compounds is also limited and is believed to extend only over the units of [M(X)(CN)6]-6+X, wherein X is the oxidation state of the transition metal and is in general +2 or +3. It is desirable to provide compounds wherein the pi delocalization is extPn-led further than that of the copper oxide-planes to obtain novel electronic yloy~,l Lies.

SUMl~RY OF THF. I~VF~TION
It is an object of the present invention to provide devices co.. ~ ;.. g and m~th~ tle of use co.,l~ g photom~gnPtic m~t~ l that incleases local magnetization after being irradiated with light.
The devices and methods of use include optical con~y~ and com,uuhl disks, both with read-write capability and random access memory; light weight motors; m~n~tic analog films, tapes or subsL a~es; digital films, tapes or substrates; optical switches;
photocopiers and sensors.
There is provided by the present invention the use of y~ ed planar compounds comprising transition metals selected from the group consisting of Ni(II), Pd(II), Pt(II), Au(III), Ir(I), Rh(I), and three tlim~nejonal compounds cn,..y~ ;~;.-g transition metals selected from the group con~ieting of Fe(II), Fe(III), Co(II), Co(III), Cr(III), Mn(II), Mn(III), Mo(II), Os(II), Rh(III), Ru(III) and Ir(III), wherein the infrared spectra of these compounds have a fing~lylhl~ peak within the range of 595-655 cm~l for the metal-carbon stretch. In ~ fell~,d embo.l;...~ , the co.llyoullds are f~ll.,magnetic, comprise nickel, iron or cobalt, have a density below 5 g/cm3 and show enh~nred ~llu...~nP,tiem when exposed to light or thPrm~l energy. Planar compounds such as those comprieed of nickel have a density below 5 gm/cm3. Three fiimPneional compounds such as those comrriein~
Fe or Co have a density below 3 gm/cm3.

~1VO 97/36294 PCTtUS97/05401 B~TFF ~F~Cl~pTION OF THF. T)F~ GS
Various other objects, features and ~ttenr~ t advantages of the present invention will be more fully appreciated as the same becomes better understood when considered in conjunction with the accolllp~,ying drawings, in which like ~cr~,~;nce characters ~lecignstt~P
the same or similar parts throughout the several views, and wherein:
Figure 1 depicts the prior art magneto-optical read-write mech~ni~m Figure lA isa sçhem~tic depiction of the method used to write to an MO disk. Figure 1 B is a schematic depiction of the method used to read an MO disk.
Figure 2 is a s~h~ n,. I ic of top view of a .~ .~g. ,- lic tape or substrate onto which particles of PM and NFM have been blended uniformly into a tape or ~-lb~Ll~L~.
Figure 3 is a s~h~m~tic of cross section of PM coated onto a layer of NFM such as in a floppy disk or co~ uhl disk.
Figures 4A and 4B depict the mech~ni~m of action of storage of information in the device depicted in Figure 3. In Figure 4A an applied m~gnP,tic field traverses the PM and NFM layers. Note that the NFM domains are randomly oriented at right angles to the applied m~gnetic field. Note that the applied m~gnPtiC field is less than BCritjCa~. This is the blank storage meAillm In Figure 4B, the ~res is applied to one NFM dom~in, producing a region of inrillced m~gneti~m (or, ~nh~n~e~l local m~gn~tic field) at the cl- m~in, raising B~oca~ above BCrj,jCa, and causing polarization of the domain.
Figure 5 is a sçhPm~tiC of an optical switch. The polarization (P) of light signal (B) is altered by light signal (A).
Figure 6 is a lepl~se~ lion of the partial atomic structure of a planar compound for use in the present invention.
Figure 7 is a l~l,lL,s~ ;on of the partial atomic structure of a 3-D compound for use in the present invention.
Figures 8A-C are lep~e ~ ons of possible st~c~ing arrange.llellt~ for planar compounds for use in the present invention.
Figure 9 is a ,e~"es~ n of the atomic ~ll u~ ; of a planar compound for use in -- the present invention with cations shown.
Figure 10 is an infrared spectrum of a compound for use in the present invention.

CA 02248602 l998-09-ll WO 97/36294 PCTrUS97/05401 nFTATT.F.l ) nF~CRIPTION OF THF p~F.FF.RRF.T) Fl\~PsOnI~F.~TS
As used herein, "photom~netic ni~tPri~l (PM) refers to any m~tPri~l that ~h~npesits magnetic ~lopellies when exposed to light of a particular wavelength and intensity.
As used herein, "resonance wavelength" (~res) refers to the wavelength of light that m~ximi7es a photo-in~ ce~ effect.
As used herein, "normal fel~u~.AgnP,tic material" (NFM) refers to any m~tPri~l that can be perm~nPntly m~_n~ti7.P~l As used herein, "optical switch" refers to and optical switch in a true optical co~ ,uL~,l and refers to a device capable of allowing one light signal to change a lJrol)~,.ly of a second light signal. Such plo~ ies include, but are not limited to, phase, polari_ation, and frequency. Preferably, the change is one that is readily measurable.
The invention encomp~cces applications including, but not limited to, (1) lightweight ferrom~_nPtic applications, COIIIInIIeI and data storage technology; (2) recording technology; (3) photocopying devices, (4) optical switches; (5) m~gnPtiC analog film; and (6) electronic devices and sensors.
It is now possible to improve on previous devices incoll,o~dliilg MO m~teri~l~ by using m~tPriRl~ that have a true photu~ g..elic propelly. The areal density of these m~t~ri~l~ is limited only by the width of the laser beam, the wavelength of light and small effects due to the sc~ . ;.,p. of light at the substrate surface. This can lead to effective storage areas a few orders of magnitude smaller than what can be ~ lclllly achieved with current MO systems. A second improvement is the speed at which information can be stored by the m~tPri~l This can be realized when PM m~tPri~l~ are chosen that have mech~nicm~ that are electronically based. Electronic excitations ind~ced by the absorption of light generally occur on a sub-n~nosecond tirne scale m~kin~ the alteration in m~gnPtic properties of these materials several orders of m~_nitllde less than ~ cllLly used compounds.
The use of electronically based photom~_nPtic effect m~te~ to accompli~h optical switching makes possible the use of optical cUlll~ since the switches would -~ intrinsically operate on s-~bn~n~ second time scales.
With respect to the photom~pnPtic effect, PMs are suitable for use in optical computers. The compositions described herein are the prcr~llcd PMs as they are one of the few known materials with the potential capability of converting light infi rm~tion into CA 02248602 l998-09-ll W O 97/36294 11 PCT~US97/05401 m~n~tiC hlro~ ation. Although infor nation can be tr~n~mittp~l optically, it must still be stored magnetically. Thus, the optica~ co~ industr~ has been searching for m~tPri~l capable of acting as the interface between light-based systems and m~gnP,tic data storage systems.
In addition, the fact that the PMs respond m~gnPtically to light creates the potential for "read-write" CDs that can be written on with laser light, then erased and re-used.
Current read-write technology is heat-based and is thus less accurate and disks deteriorate faster than a lower-lclLIl.c~ c technology that uses the photom~netic effect.
The light weight of the PMs means that they are suitable for use in all devices where m~gnt-t~ are l.leselllly used and the weight ofthe device is important. Magnets made co~t~ining PMs weigh subst~nti~lly less than traditional m~gnPt~ Thus, m~gnP,t~
made from PMs are suitable for use in the motors of electric cars, aircraft and portable devices where weight is at a premiurn.
Derivatives of particular photom~pnPtic m~tPri~i~ can be made into normal ferrom~gnetic m~t~ri~l~ which are ferr m~etic without the ~C~i~t~nce of light. U.S. Pat.
No. 5,501,808. These m~t~ori~l~ have very low physical ~nCiti~S but still have leasonably large magnetic densities. These light weight m~C~t~ are suitable for use in m~chines where weight is a critical factor such as motors for electric cars, aircraft and portable devlces.
Recor~ g t~rhnolo~y. A potential application is the development of a tape or film impre~n~ted with photom~pn~tic particles that will respond directly to light and form a m~gnetic image. In the fields of audio and visual leco/diLrcg, the digital code can be written on the tape with a laser beam, thus increasing the amount of h~llll~lion that can be stored on the tape. Laser beam technology is already well-developed in connection with CD-ROM technology, so adapting it to PM-based technology should not present any great technical obstacles. In addition, in the field of visual recording, an image may be capable of being captured directly in analog form on the PM-impregn~te~l tape, i.e., the image is actually c~ d m~gnetically. This is analogous to the traditional motion picture celluloid film process where the image is stored 'in a direct, one-for-one ~ipl~s~ ion on the film by a chemical process. With the PM-based technology, however, the tape has the potential to be re-used and readily edited like m~g~Ptic videotape.

~gnetic Irformation Stor~ge. Recording and accessing hlro"llalion on photomagnetic m~-linm can be accomplished as follows.
As depicted in Figure 2, the PM particles (le~.~sel-led by Xs in Figure 1) are combined with the NFM particles (~ lcsellled by Os in Figure 2) into a tape or substrate.
In an alternate configuration, the PM is coated onto a layer of NFM as depicted in Figure 3.
Information is placed onto the material as follows:
Referring to Figure 4A, the ~ Jal~;d composites are placed in an applied m~gnptic field (Bapp~jed) that is less than the critical magnetic field (BCntica,) required to m~gn~tir~lly polarize a NFM domain parallel to the applied field. As shown in Figure 4B, when light at the resonance wavelength (~res) is applied to a single point on the surface or the entire surface co. ~ g PM, the magneti_ation vector of PM incleases. This increases thestrength of the local applied m~gnetic field (B~ocal) acco..lillg to the relationship Blocal res)Bapplied~ where ~(~res) iS defined as the photo-in~ ce~ m~pn~tic perm~flbility of PM.
The B~ocal is made greater than BCritica, and this in turn in~uce~ a m~netic pol~ri7~tirJn vector parallel to the applied field in the NFM domain at that point. The cross h~trhed area in Figure 4B indicates the region of intl~lced or enh~nred local m~gn~ti7~tion.
IlTadiation with ~res causes one NFM domain to align with Bapp,jed. This domain contains magnetic information. This process occurs at close to the speed of light. This process can be reversed by reversing the applied m~nrtic field. In Figure 4, the applied m~gnrtic field can be applied at any angle. Likewise, the light beam can be directed at any angle to the PM.
The m~gnetic information can be ~ccessecl by moniL~ ,i,.g the polar Kerr rotation of a light source reflected from the surface of the composite. P~ bly, the light source is not at ~res, or, if at Ares~ it is below the critical illlel~iLy.
Forrning analog magnetic images is accomplished as stated above except that the gray and color scales can be ~c~sellled by variations in the m~ti7Ation vector at dirr~ points on the surface. These variations are in~ ced by variations in light hll~llsily --~ (gray scale) and wavelength of light (color scale) ~It~ring the magnitude of ~ res), which is a function of both these variables. This in turn sets the m~gn~ti7~tiQn vector in the NFM
domains at each point forming an analog m~gn~tic image.

Photom~nPtic m~tPri~l.e can be used in the field of visual l~cordi~lg. Images can be captured directly in analog form on a tape or substrate hnpleg~te~ with a photom~enetic compound, i.e., the image is actually c~luled m~enetically. This is ~ analogous to the traditional motion picture celluloid fiLm process where the image is stored in a direct, one-for-one representation on the film by a chemical process. With this new technology, however, the tape has the potential to be re-used and readily edited like m~enPtic videotape.
Photocopying technolo~. Another application is the development of a new photocopying process. Current photocopying plocesses use light-sensitive m~tPri~l~
combined with electrostatic charge to guide the ink onto the copy surface. Using the same conceptual approach, photomagnetic m~tPri~l~ combined with m~enPtic fields can be used to guide the ink onto the copy surface.
Flectronic devices ~d s~n~ors. Sensors are used in a ubiquitous fashion throughout industry. When used as a light sensor, photom~çtic m~tçri~lc are moreversatile than a photodiode. Photom~e1lPtic m~tPri~lc can respond to light hll.,.lsily, m~nPtic field ~L.eng~l, tempe~ e and wavelength of light. U.S. Pat. No. 5,501,808.
This is in contrast to photodiodes which in general respond only to changes in light i~ltel,~iLy and a limited range of wavelengths. When photomagnetic m~tPri~l ~ are combined with applied m~nPtic fields, the wavelength of light that they respond to can vary with the hl~ y of the applied m~gnPtic field. Sensors made with these m~terj~l~
can respond to specific frequencies of light.
Any electronic devices which plesen~ly rely on ferromagnets are ~ubsl~lially enh~nl~ed by using photom~enPtic m~teri~l In most electronic devices, the electron speed is about 1% of the speed of light, while optical signals travel at 90% of the speed of light.
Thus, using ferrom~gnPts that can respond to optical signals yl~se.lls obvious speed adv~nt~es The photom~nP-tic material also plCs~ a new way of ~letecting light, m~enetic fields and/or combinations thereo~ As a light sensor, it would be more versatile than a photodiode. Prel ;l. .in,.. y testing indicates that the threshold frequency of light -~ which produces the photom~enPtic effect appears to vary with the ~l~ellglll of an applied m~enPtic field. The sensor could thus be "tuned" to react to dirr ~ell- frequencies of light.
This is in contrast to photodiodes, whcl~i;n dirrel~ m~tPri~l~ need to be employed for each frequency range.

CA 02248602 l998-09-ll W 0 97/36294 1~ rCT~US97/05401-Optical Switrhi~. Optieal ~ chillg can be achieved as follows. As depicted in Figure 5, a layer of PM is placed in an applied magnetic field. A light signal (A) that is at ~rcs is incident on a point on the PM layer while a second polarized light signal (B) is reflected from the same point as (A). The in~ll)ce~ m~EnPti7~tiQn ~ res) ofthe PM causes the polarization of signal (B) to change via the polar Kerr rotation effect.
There are a number of products where it is vital to have the lightest possible electric motor. For exarnple, electric cars need to have very lightweight electric motors in order to conserve energy and run efficiently; any extra weight makes them inefficient and costly to run. For example cars powered by electric motors with m~gn~te made from PMs would be more efficient and able to travel longer fiict~n~es Another example is portable audio and video lccoldillg devices. The market clem~n-lc that these products be as light and compact as possible. Each device, however, has to have an electric motor to roll the video or audio tape through the m~ in~. Because it must contain a m~gn-o.t, the motor is one of the heaviest co."ponents in these devices and PM will reduce that weight s-lbst~nti~lly.
The two primary applications in the co~ u~ /data storage market are: (1) high speed optical computers and (2) laser-me~ te~l data storage. An integral part of the optical co~ u~el is a so-called "optical chip" which uses light instead of electronic signals.
Ordinary floppy disks use m~pnPtic storage to store approximately 2 megabytes ofdata. Optical disks can store up to 600 megabytes of data. The drawback of conventional optical disks (such as CD-ROM disks) is that, unlike m~gnetic disks, they cannot be erased and re-recorded with new data. Thus, over the past ten years, the data storage industry has been developing MO disks which store the information m~gn~tically like a m~gnetic disk and can thus be erased and re-written, but which can be read and written on with light, thus permitting the much higher data storage capacities of optical disks.
MO disks are currently being m~mlf~ctl-red and sold primarily by Philips and Sony, which also make the drives necess~ry for reading and writing on such disks.
P~s have applications in the area of MO disks. The current m~g~to-optical disks ~- work by a heating process which is relatively inefficient. Recording takes place via a high-power writing laser which quickly warms a tiny area on the disks metallic surface, c~.leing the m~gn~ti7e~ molecules to line up with the magnet below. On playback, a specially filtered low-power laser beam strikes these molecules and is altered slightly as it bounces off the disk. The reflected light is the~ converted into an electronic signal. To erase, the m~chin~ry simply reverses the current in ~he magnet, the writing laser comes back on, and the molecules get flipped the other way.
Because PMs can become ferromagnetic in the presence of the correct frequency ofS light, and because ferromagnetic materials can in turn enhance the strength of a m~gn.-tic field, a m~gn~tic disk surface can be impregn~tec~ with PM such that a writing laser will increase the m~gn.-tic field in the area where the beam strikes to a critical strength, causing that region, and that region only, to "flip" as in the conventional magneto-optical disk.
This process, however, uses no heat, so the in~ffici~ncies of heat l~al~Ç~l (e.~" slow speed, poorer resolution of the bearn-affected region, breakdown of m~t~ri~l~) are avoided.
Reading is ~ccomplished exactly as in the current heat-based technology. Fr~ing is simpler and more efficient than with the current heat-based systems, since the en~ire disk is simply exposed to light in the presence of the reversed m~gn.otic field instead of being heated in the presence of the reversed field.
The invention includes the use of compounds with only one transition metal as well as those with mixtures of transition metals having the same coor~lin~tion ch~ct~;. ;ctics which form either planar or 3-D structures. The molar ratio of the tr~n~ition metals within the compound can vary widely. A continuous ratio of mixing is possible. Mixed transition metals have been shown in the planar Hofmann clal~llales described by Iwamoto, supra;
~he "Prussian Blues" described by Shriver et al., supra, and the poly(yne) compounds describedbySonogashiraetal.,J. Organomet. Chem. 160:319-327(1978). The compounds of the present invention comprise transition metals as described above in a coordinated crystal structure such that a metal-carbon stretch provides a broad fingei~lmt peak within the range of 595 to 655 cm l within its infrared spectra. The hydrated form of the crystalline-like compounds of this invention which comprise nickel have a finge~ L
peak of about 625 cm-~ in the IR spectra and a finge.~llnt peak of about 7.98 A in the X-Ray powder diffraction spectra.
The tr~n~ition metals useful in forming the crystalline-like compounds having a planar structure are those capable of forming square planar complexes such as Ni(II), Pd(II), Pt(II), Au(III), Ir(I) and Rh(I). Such transition metal species provide bonding angles of 90~ and 180~. The transition metals co.lle~ t~cl for use in crystalline-like compounds having 3-D networks are capable of fonning octahedral complexes with .. . . .

W O 97/36294 PCTrUS97105401 carbon. These include Fe(II), Fe~III), Co(II), Co(III), Cr(III), Mn(II), Mn(III), Mo(II), Os(II), Rh(III), Ru(III) and Ir(III). These transition metals provide the a~lo~liate bonding angle con~i~tçnt with copper oxide planes. In forming the transition metal planes or three-tlimton~ional network, the transition metal is reacted with a coor~ compound or ligand to complete the crystalline structure of the compound.
The unit cells for these crystalline-like compounds can be planar or 3--iim~?ncional, depending on the transition metal used. The si_e of the unit cell also varies with the transition metal(s) ~ltili7~1 Two axes (a and b) for the unit cell of the planar crystalline structure have a 11im-on~ion which is a multiple of a value in the range of 4.90 A to 5.10 A.
The value multiplied tlepPn(lc on the transition metal due to the varying size ofthe bond lengths. The multiplier, N, is typically from 1-1000, more typically less than 100.
Therefore, the range of ~imemions for the axes a and b can be l~ s~ ed as 4.9 A N to 5.1 A N. The axes a and b do not have to have equivalent ~im~n~ions. The ~ t~n~ebetween the planes can vary from 3.5 A to 4.5 A for non-hydrated compounds and 3.5-10A
for intercalated or hydrated compounds. The C axis is some multiple ofthe flist~n~e between planes. For nickel compounds, the rlim~ncjons of the two axes a and b are both about 10.13 A (N = 2) and the (li~t~nce btLv~ el1 planes is believed to be about 6.75 A with a C-axis of about 13.5 A.
The unit cell for three ~lim~n~ional compounds have axes a, b and c with fiimencjons l~ esell~ed by multiples of a value in the range of 4.9 A to 5.1 A, depending on the transition metal. The multiplier, N, is also typically from 1-1000, more typically less than 100. Therefore, the range of dim~n~ions for the axes a, b and c can berepresçntçd as 4.9 A N to 5.1 A N. The axes a, b and c do not have to have equivalent tllm~n~lons.
Where more than one transition metal is used and the compound is crystalline, the ~iimton~ions of the unit cell are expected to fall within the ranges above. However, with mixed transition metals, the compound's structure may be completely random with respect to the order of transition metals with no definable unit cell.
- Not wishing to be bound by theory, it is believed that the transition metal iscoordi,lalt:d with acetylide, C22~, se~ ; This theory is c~n~i~t~nt with the products expected from the starting materials utilized in forming the transition metal crystal structures; the size of the unit cell of crystalline-like nickel compounds, as extrapolated . .

from X-Ray powder diffraction data and the unique electronic IJlUp~,l lies of the compounds obtained. Pursuant to this theory, a partial unit cell (counter cations not shown) for a four coordinated transition metal bonded to acetylide has the structure shown below:

C
C

wherein Mc(Y) = a four coordinated transition metal. An example of a partial unit cell (counter cations not shown) for a six coordinated transition metal bonded to acetylide has the structure shown below:
C c,~

1 5 -CjMc(Y)-c-~C C

Not wishing to be bound by theory, it is believed the planar crystalline transition metal compounds of the present invention are of a structure as shown in Figure 6, where only transition metals 5 and acetylene carbons are shown. The counter cations are not shown in Figure 6 and are believed to extend between the planes. The empirical formula for compounds with a structure as shown in Figure 6 is M(X)(4.~ XMC(Y)C4, wherein MC(Y) is the transitiûn metal, with Y being its ionic state and M(X) being the counter cation with X being its ionic state. M(X) is typically an alkali metal, ~lk~line earth metal or rare earth metal or stable cation such ~ a 4~ mmonium ion (NR4+) where R is H or any organic moiety. Such a structure will provide a delocalized pi system over a signifiç~nt portion of the compound. Planar compounds of the formula M(X)(4 Y)~XMC(Y)C4n wheleill n = 1-6 will also provide a delocali~d pi system. In such a compound, more than one acetylene group is bonded between the metal atoms.
In the crystalline compounds of the present invention having three ~~imçn.~ionalcrystal structure, the coorrlin~ting con,l)o~ ds or ligands extend b~ ,el~ planes. Not -~ wishing to be bound by theory, where the coortlin~ting colnpu~ld or ligand is an acetylide (C22~), it is believed the 3-D crystalline network has a structure as shown in Figure 7. The empirical formula for such a crystalline compound is M(X)(6 ~,"XMC(Y)C6, wherein MC(Y) is a transition metal, with Y being its ionic state, and M(X) being the counter cation with X

CA 02248602 l998-09-ll being its ionic state. Three tlim~ onal compounds of the formula M(X)(6.y"7~Mc(Y)C6n wherein n=1-6, also provide a delocalized pi system.
As shown in Figures 8A-7C, the planar structures can have many orientations including eclipsed, staggered or centered. The eclipsed form, shown in Fig. 8A, makes the planes sup~ osed and is a tetragonal unit cell since a=b~c and the bond angle a=~=~=90~. The c axis is given as the interplanar distance. This type of geometry has been seen in certain transition metal cyanides as disclosed by Miller et al. (1975) Prog Inorganic Chem. 20:1. The staggered form, shown in Fig. 7B, has many combinations and places the planes at some orientation other than eclipsed or cen~led. The sequence could be ABA where the A planes are in the same orientation and the B planes are staggered. A
special case of staggered is centered, shown in Fig. 7C. In this case, the c axis is twice the interplanar distance.
When the counter cations are considered in the structures given in Figures 6 and 7, the unit cells will remain in the tetragonal crystal system if their arrangement is the same for each unit. When the counter cations have repeat p~ltern~ that encolll~ass more than one unit, then the crystal system can change. When the pattern is only along the c axis, the tetragonal system is "~i.; "~ 1 If it is along either the a or b axes, then the system can become orthorhombic wherein a~b~c; however, a=~= y=90~.
When con.ci~1~ring the crystal ~ILu~;Lu,cs for the 3-D nclw~ lks as shown in Figure 7, it is usually seen that the cell unit is cubic without consideration of the counter cations.
(a=b=c and a=,B=7~=90~). This would be true because the connectivity is the same along three crystallographic axes. When the counter cations are considered, the crystal system can become either tcll~gollal or orthorhombic, depending on the direction of the counter cation repeat pattern.
Dimeric and oligomeric forms of these proposed compounds have been synt~Psi by Takahasi et al. The Institute of Scientif c and lndustrial ~esearch, pp, 247-251. The compounds of the present invention are more deloc~li7e.1 and partially ionic in character and thus have stabilities greater than known non-ionic linear transition metal acetylide -- polymers. The compounds, described herein, like the linear transition metal acetylides, can obtain high molecular weights. However, the compounds of this invention are two-dimensional and three-rlimen~ional in slru~ e with many compounds being ceramic-like.

... ..

Compounds of the present invention can be produced by reacting anhydrous transition metal halide with alkali metal and/or ~lk~line earth metal acetylides (C22~ =
acetylide) in an inert atmosphere following mixing at a temperature of at least 300~C, preferably at the eutectic tel~lpeldlu~e of the transition metal halide and the alkali metal/~lk~line earth metal halide for at least 3 ~ es to more than one hour. Forexample, the eutectic tClllp~ldlU.c of NiCI2 and CaCl2 is about 600~C. Two or more transition metal halides can be reacted to provide compounds with mixed transition metals.
A mixture of black and white powder is obtained from this reaction. The formation of a black powder is noticed as the reaction progresses until a color change is complete. This method was used to prepare the crystal-like compositions ofthis invention compri~ing nickel with the following stoichiometry NiCl2(s) + 2CaC2(s) ~ CaNiC4(s) + CaC12(s) A more general formula is as follows:
Mc(Y)Zy + 2M(X)2,XC2 ~ M(x)(4-y)lxMc(y)c4 + YM(X)Zx where Z is a halogen.
This method is pl~;rell~;d and preferably, the reaction volume is ~ rd to l--i--i-lli7e sublimation loss of NiCl2. Purification ofthe product is ~ccoTnplished by extracting calcium chloride and unreacted nickel chloride with an alcohol. Calcium carbide can also be removed by reaction with an alcohol. The planar structure and the presence of acetylide ligands are con.~i~t~nt with X-Ray powder diffraction analysis.
Other methods are also suitable, such as reacting within a solvent a transition metal tetraacetylide complex of the formula M(X)(4 y)/xMc(Y)(C2H)4 and a transition metal salt of the formula M(X)(4 y)~7~Mc(Y)Z4 in the presellce of a catalyst such as a copper (1) salt of the formula Cu(I)Z, AgC103, AIBN or Bu3B/02, wherein M(X) and MC(Y) are as defined above and Z is preferably a halide or carboxylate. Two or more transition metal halides and/or two or more transition metal tetraacetylide complexes can be reacted to provide compounds with mixed transition metals.
An additional method for p~p~illg a metal compound having a 3-D crystalline -- structure comprises reacting within a solvent a transition metal he~cetylide complex of the formula M(X)(6 ~ XMC(Y)(C2H)6 and a transition metal salt of the formula M(X)(6 y)"~MC(Y)Z6 in the presence of a catalyst such as a copper (1) salt of the formtll~ Cu(I)Z
(where Z is preferably halide or carboxylate) AgCl03, AIBN or Bu3B/02. In pler~ ed CA 02248602 l998-09-ll W O 97/36294 PCTnUS97/OS401 embo-lim~ntc, the transition metal is nickel. Two or more transition metal halides and/or two or more transition metal tetraacetylide complexes can be reacted to provide compounds with mixed transition metals.
The tetraacetylide complex can be obtained by a novel method of this invention wherein acetylene is reacted in a solvent with a transition metal salt of the formula M(X)(4 y),XMC(Y)Z4 in the presence of a catalyst such as a copper (1) salt, Cu(I)Z (Z = halide) AgCl03, AlBN or BuB/02 according to the following reaction M(X)(4 y)/xMc(Y)Z4 + 4H2C2 ~ M(x)(4~y)/xMc(y)(c2H)2+4Hz-The h~ cetylide complex can be obtained by a similar reaction scheme with the sarne catalysts wherein equivalents of acetylene are reacted in a solvent with M(X)(6~y)/xMc(Y)Z6 to provide M(x)(4-y)/xMc(y)(c2H)6-Alternatively, the tetraacetylide complex can be obtained by conventional means,such as reacting a transition metal thiocyanate or cyanide with an alkali earth metal salt of acetylide in solvent. The hexaacetylide complex~s can be obtained by similar techniques wherein a corresponding transition metal thiocyanate is reacted with an alkali metal salt of acetylide.
These are only some examples of methods for ~ miG~lly linking to tr~n.~ition metal atoms with acetylenic carbons. The most useful types are copper salt catalyzed reactions (Cu(I)Z) between transition metal complexes and acetylenes. This works well for Pt and Pd but not for Ni since the complexes form l)recipil~Les in amine solutions. The choice of Z is preferably limited to halides or possibly sdluldled carboxylates. The most stable catalyst is copper (1) iodide. These reactions should be carried out in the absence of ~2 since oxygen can cause oxidative coupling between the acetylides.
When transition metals having rG~ gn~tic plu~e.lies are used in the crystalline-like compounds of the present invention, these crystal structures also exhibit ferrom~gn~tic behavior. They are of low density, typically below 5 g/cm3 for planar compounds and below 3 g/cm3 for 3-D compounds, and also exhibit unusual electronic behavior.
--~ Photoferromagnetic and thermofe,l~ n~tic plol)GIlies have been found to exist in coll~po~ulds comprised of nickel. In addition, a nonlinear ferromagnetic response with respect to an externally applied magnetic field has been found.

WO 97/36294 PCT~US97/05401 The compounds cont~inin~ ni$kel have been obtained by heating nickel chloride and calcium carbide in an inert atmosphere following mixing and heating under the conditions described in the examples. The nickel compound is hygroscopic and reacts with a large excess of water to produce a ~ lul'c of nickel hydroxide, calcium hydroxide and acetylene gas. The hygroscopic formula being CaNiC4-xH20 WllClcl~lXis believed to be between 2 and 0. The nickel compound is black with a metallic luster and has a bulk density of dpploxilllately 1.34 grams per/ml. The compound catalyzes the decomposition of diethylether.
Ferrom~gneti~m is in~lced or enh~nce~l by irra~i~ting a sample of the PMs described herein with either fluorescent light or sunlight with an optimum wavelength between 600 and 400 nm. The light is plcf lably provided by laser so as to adjust the spot size. The spot size is limited only by diffraction effects, wavelength and anomalous scattering effects. These are negligible and easily controllable. Ferrom~gntoti~m is infl~lce~l or e~h~nced by heating a sample to at least about 20~C, preferably 70~-90~C. Higher tenlp.,ldlules provide a stronger rcalJollse. The fello~ gn~tic compounds show a non-linear ferromagnetic response with respect to ext~rn~lly applied m~pn~tic fields with the response increasing with increasing fields. Not wishing to be bound by theory, it is believed that when the conduction band reaches a critical electron density, the ~xçh~r~e interaction inrluces the ferromagnetic transition. This critical electron density can be reached by either photon excitation or by thermal excitation or both. The energy gap of the material is a function of the applied extemal m~n~tic field and decreases as field strength increases since the energy of the conduction electrons are lowered. This applied extern~l field can be coupled with the excitation of electrons with photons or thermal energy. The material is either semicon~ cting or sçmimet~llic.
Not wishing to be bound by theory, it is believed that the structures and stoichiometry of these compounds is indicative of a supercon~lctinp transition within these compounds at some t~nll,el~ e. It is also believed the mixed transition metal compounds will provide electrical prop~ ies dirr.,lenl from those compounds having only -- one transition metal. For example, a compound with Fe(II) is expected to be semi-con~lcting based on a diagram of its molecular orbitals and a compound with Fe(III) is expected to be con~lllctin~ A compound with both Fe(III) and Fe(II) would transfer from semiconductive to a metal-like conductor as the proportion of Fe(III) is increased.

W O 97/36294 22 PCT~US97/05401 Metal-like compounds are expeoted to have 60-100 mol% Fe(III) and semimçt~llics are expected to have 0-60 mol% Fe(lll).
Without further elaboration, it is believed that one skilled in the art can, using the prece-ling description. utilize the present invention to its fullest extent. The following plcielled specific embo~im~ntc of the p,erellcd composition are, therefore, to be construed as merely illustrative and not imitative of the rçnn~;nfler of the disclosure in any way whatsoever.
In the foregoing and in the following examples, all ten~eldlules are set forth uncorrected in degrees Celsius; and, unless otherwise indicated, all parts and pel~;ellldges are by weight.
The entire disclosures of all applications, patents, and publications, cited above and below, are hereby incorporated by reference.

F~l~/IPT .~.
Nickel chloride and calcium carbide in a 1:2 molar ratio in a solid state (anhydrous) were heated with a protective argon purge gas at 1 atm in a quartz reactor. The crucible was open to the purge gas. An electric oven was used to provide a telll~ldlule of about 970~C for 24 minlltes During h~ting, a color change in the starting m~f~ri~l~ was noticed after two minlltes and, following 24 ~ s, the color change was complete. Following h~ting, the re~ct~nt~ were washed with distilledldeionized water for one hour to remove the soluble salt byproducts and unreacted starting m~t.ori~l~ such as CaCl2 and NiCl2 and also to remove excess CaC2. The product was then dried for several weeks in a desiccator.
The product was anhydrous after hç~ting The resulting product was plated out to provide a shiny black/white powder with a density of about 1.8 1 0.5 g/cm3. The compoundrem~inç~l inert for about one year with no oxidation, even when heated to a temperature of about 70~C. When added to diethylether, the solution bubbled, showing indications of a reaction without a loss of material, suggesting catalysis. The combustion te~ dlul~ was found to be about 200~C-300~C which yielded a green and white powder.
An IR spectrum and X-Ray dirrl~.;lion ~cc~ 1 were taken of the anhydrous product. Diffraction and IR spectra showed the ~l~,sellce of Ca(OH)2, CaC03 and Ni metal and nn~ l peaks attributed to one of the inventive compounds in the lllixlule. The Ni ~VO 97/36294 23 PCT/US97/05401 metal may have been formed by decomposition of NiCl2 since it is known that the ionic salt carbides reduce transition metal halides at tC~ C~ cs of about 700~C.
The IR Spectra Figure 10 is the IR spectrum of a compound produced by the method above. The S broad band from 3000-3600 cm~~ is ~ccign~d the OH stretch of Ca~OH)2 and possibly water of hydration. The broad band at 1200-1400 cm~l is ~ccignecl to CaC03 and Ca(OH)2.
The two bands at 2924 cm I and 2~75 cm~~ correlate with the compound K2Pt(C2CH3)2.
However, the bands are due more likely to the analogous species such as M(X)2,,CNi(C2R)4 on the surface. These compounds are most likely formed by reaction with impure acetylides present in CaC2. The peak at 2349 cm~l is C02. The peaks at 1087 cm~l (Hl), 875 cm-~ (H2) and 712 cm l (H3) are CaCO3. The jagged bands at 3600-4000 cm-~ and 1600-2000cm-l arefreewater(12). Thepeaksat2500cml (G)and lOOOcml (J)have not been ~csigned at this time. The broad peak at 1625 cm ' (E) is ~cci~necl to water of hydration. The presence of water of hydration in the ~lJCc~ may indicate the unknown material is hygroscopic, since Ca(OH)2 and CaCO3 do not form hydrates. The band at 625 cm~' is believed to be Ni-C stretching. The approximate location of a nickel acetylenic carbon stretch in free molecules is 585 cm~l, and, therefore, this black powder product does not comprise free molecules.
X-Rav n;ffraction An X-Ray powder diffraction pattern was recorded and an elem~nt~l analysis was also done. Confining the powder diffraction file search with the elem~nt~l analysis allowed for identification of Ni metal, calcium hydroxide and CaCO3. The intense lines rem~ining define a compound of the present invention. This showed a low ill~en~ily line of 7.98 A. The elem~nt~l analysis showed the pl~,sence of Ca, Ni and lesser amounts of Cl and Mg, some Si, Al and S. The spectrum was recorded on an electron microscope equipped for el~m~nt~l analysis. However, this procedure did not allow for identification of carbon.
Figure 9 shows a rc~rece~ I ;on of the ~ u;Lu~e of a tcll~calbide, the transition - - metals 5, acetylene carbons 15 and cations are shown but the water molecules are not shown. A tetragonal unit cell with a = b = 10.13 ~, c = 13.25 ~ is in-~e~eCl from the X-Ray diffraction powder pattern taken of the compound formed. The ~imenCions of the a and b . . ... . , ... ~ . ... . .

W O 97/36294 PCT~US97/05401 axes are con~i~tent with the experimental data on the bond lengths and bond angles of nickel acetylides.
The compound was found to be ferromagnetic with the ferrom~gnPtic proyellies being in~ ce~l or enhanced upon exposure to fluorescent light or sunlight. The ferrom~gnçti~m was Aenn~ .dl~d visually. The compound was also found to have ferromagnetic properties which persist after irradiation as long as 1-3 hours, showing a gradual decay.
The compound is also thermom~g~tic. Heating the compound to about 70-80~C
in-ln~ecl or enh~nce~l magnetic l,lo~ ies. Th~rmom~netism is found at t~ lp~ S of 20~C and higher.
Exposing the compound to a magnetic field also enh~nced fcllolllagnetic behaviorin response to light and heat. Exposure to high magnetic strengths allowed inc~nrlescçnt light to induce ferromagnetism. Ferrom~gn~ti~m in~ ced under these conditions is shown with the same test m~En~tc used to show ferrom~n~ti~m under fluolescel.l light. Not wishing to be bound by theory, high m~gnetic field strengths are expected to reduce the band gap, allowing such frequencies to provide the desired response.
The compound is a black material with a strong metallic luster. It is ferrom~gnçtic on the same order of magnitude as iron, but with a density of 1.34 g/cm3. This means that it is the lightest known ferrom~gn~-tic material, and weighs less than 2~% of the weight of better known ferrom~gnçtic materials such as iron.
The prece~ing examples can be repeated with similar success by s~lb~ g the generically or specifically described re~cl~"l~ and/or operating conditions of this invention for those used in the plece~ g examples.
~rom the foregoing description, one skilled in the art can easily ascertain the essçnti~l characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

Claims (18)

WHAT IS CLAIMED IS:

1. A method of recording information on a magnetic medium, the magnetic medium including a number of magnetically polarized local domains and photomagnetic material adjacent to the magnetically polarized local domains, the method comprising the steps of:
placing the magnetic medium in an applied magnetic field; and applying light to a first location of the magnetic medium to induce magnetization of the photomagnetic material at the first location, wherein the magnetized photomagnetic material is adjacent to a first magnetically polarized local domain, wherein the magnetization of the photomagnetic material increases the strength of the magnetic field at the first location by a first amount to change the polarization of the first magnetically polarized local domain.

2. The method of claim 1 further comprising the step of:
applying light to a second location of the magnetic medium to induce magnetization of the photomagnetic material at the second location, wherein the magnetized photomagnetic material is adjacent to a second magnetically polarized local domain, wherein the magnetization of the photomagnetic material increases the strength of the magnetic field at the second location by a second amount to change the polarization of the second magnetically polarized local domain, wherein the first amount differs from the second amount, and the change in the polarization of the first domain differs from the change in the polarization of the second domain.

3. A method of recording information on a magnetic medium, the magnetic medium including a number of magnetically polarized local domains and photomagnetic material adjacent to the magnetically polarized local domains, the method comprising the steps of:
(a) placing the magnetic medium in an applied magnetic field less than the critical magnetic field required to change the polarization of the local magnetic domains, (b) applying light to a particular location of the magnetic medium to induce magnetization of the photomagnetic material at the particular location, wherein the magnetized photomagnetic material is adjacent to a particular magnetically polarized local domain, the magnetization of the photomagnetic material changing the magnetic polarization of the particular magnetically polarized local domain by increasing the strength of the local magnetic field at the particular location to be greater than the critical magnetic field.

4. The method of claim 3, wherein the applying step changes the magnetic polarization of a particular local magnetic domain to be parallel to the applied field.

5. The method of claim 3, wherein the applying step increases the strength of the local magnetic field B local according to the relationship B local = µ(.lambda.)B applied, wherein B applied is the applied magnetic field, and µ(.lambda.) is a photo-induced magnetic permeability.

6. The method of claim 5, wherein µ is a function of a parameter selected from the group consisting of wavelength, temperature, light intensity and applied magnetic field.

7. A magnetic medium comprising:
(a) a plurality of magnetically polarized local domains, and (b) photomagnetic material adjacent to the magnetically polarized local domains, (c) wherein the photomagnetic material increases the strength of a magnetic field at a particular magnetically polarized local domain when the photomagnetic material receives light at a location adjacent to the particular local domain.

8. The magnetic medium of claim 7, wherein information is recorded at a particular location on the magnetic medium by (1) placing the magnetic medium in an applied magnetic field less than the critical magnetic field required to change the polarization of the local magnetic domains, and (2) applying light to the particular location of the magnetic medium to induce magnetization of the photomagnetic material at the particular location, the magnetization of the photomagnetic material changing the magnetic polarization of a particular local magnetic domain adjacent to the magnetized photomagnetic material.

9. The magnetic medium of claim 7, wherein the photomagnetic material is a compound of the formula M(X)(4-Y)/X M C(Y)C4 wherein M c(Y) is a transition metal selected from the group consisting of Ni(II), Pd(II), Pt(II), Au(III), Ir(I), Rh(I), with Y being its ionic state and M(X) is a counter cation selected from the-group consisting alkali metal, alkaline earth metal and rare earth metals with X being its ionic state; or a compound of the formula M(X)(6-Y)/X M c(Y)C6 wherein M c(Y) is a transition metal selected from the group consisting of Fe(II), Fe(III), Co(II), Co(III), Cr(III), Mn(II), Mn(III), Mo(II), Os(II), Rh(III), Ru(III) and Ir(III) with Y being its ionic state and M(X) is a counter cation selected from the group consisting of alkali metal, alkaline earth metal and rare earth metals with X being its ionic state.

10. The magnetic medium of claim 7, wherein the photomagnetic material is a layer of material coated onto a layer of a magnetic material having the magnetically polarized local domains.

11. The magnetic medium of claim 10, wherein the magnetic material is a normal ferromagnetic material.

12. The magnetic medium of-claim 7, wherein the photomagnetic material and the magnetically polarized local domains are interspersed magnetic particles in a substrate.

13. The magnetic medium of claim 12, wherein the magnetically polarized local domains are part of a normal ferromagnetic material.

14. A method of optically changing a characteristic of a first light signal, the method comprising the steps of:
(a) placing a photomagnetic material in a magnetic field;
(b) receiving a second light signal at a point on the photomagnetic material to induce magnetization of the photomagnetic material at the point; and (c) reflecting the first signal from the point on the photomagnetic material.

15. The method of claim 14, wherein the induced magnetization changes the polarization of the first signal via the polar Kerr rotation effect.

16. The method of claim 14, wherein the characteristic is a phase of the first signal.

17. The method of claim 14, wherein the characteristic is a polarization of the first signal.

18. The method of claim 14, wherein the characteristic is a change in frequency upon reflection of the first signal.