Single-crystal – oriented-crystal – and epitaxy growth processes; – Forming from vapor or gaseous state
Reexamination Certificate
2002-03-05
2004-05-11
Hiteshew, Felisa (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Forming from vapor or gaseous state
C117S054000
Reexamination Certificate
active
06733587
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to magneto-optic garnet materials having applications in optical devices such as isolators, circulators and interleavers.
2. Discussion of the Related Art
Co-assigned U.S. Pat. Nos. 5,608,570 and 5,801,875, the disclosures of which are hereby incorporated by reference, disclose magneto-optic garnet materials useful for Faraday rotator applications. As discussed therein, the disclosed materials exhibit highly desirable magnetic properties, including a substantially rectangular magnetization loop, relatively low saturation magnetization over a useful operating temperature range, and a relatively high switching field at least at room temperature. (
FIG. 1
is representative of the properties of these materials.) These materials are referred to generally as latching garnet materials, due to their ability to remain in a magnetically saturated (i.e., single domain) state. However, the garnet materials disclosed in the above patents exhibited particularly advantageous properties, due to their ability to remain latched over a relatively broad temperature range, and their ability to be “hard” latched.
(As used herein: magnetization loop is the curve of magnetization vs. applied magnetic field; a magnetization loop is “substantially rectangular” if the width of the magnetization reversal is at most 10 Oe; the “switching field” (H
s
) of the magnetization loop is the applied field at which the magnetization goes through zero (H
s
corresponds to the coercive field—H
c
of a conventional magnetization loop; “hard latching” means a switching field of 500 Oe or greater at least at room temperature.)
While the materials of the above-cited patents exhibit excellent properties, improvements in the materials and the processes for making the materials and articles incorporating the materials are always desired.
SUMMARY OF THE INVENTION
The invention relates to improvements in the production of high-performance latching magneto-optic garnet materials. It has been recognized that high-Europium magneto-optic garnets will offer superior properties in devices such as isolators, circulators and interleavers. However, formation of, e.g., (BiEu)
3
(FeGa)
5
O
12
on conventional, congruent composition, garnet substrates is difficult, due to poor lattice matching between the magneto-optic garnet and such conventional substrates. The invention addresses this problem.
The invention involves a process for forming an article, the process including steps of providing a substrate, and forming on the substrate a film of (BiEu)
3
(Fe
5−y
(Ga
x
Al
1−x
)
y
)O
12
, where x is 0 to 1, and y is 0.8 to 1.2 (with y generally selected such that the film exhibits a saturation magnetization<100 G at room temperature). According to one aspect of the invention, the substrate is a single crystal material consisting essentially of a solid solution of two or more garnet materials, the substrate having a lattice parameter within 0.004 Angstrom of the lattice parameter of the (BiEu)
3
(Fe
5−y
(Ga
x
Al
1−x
)
y
)O
12
, advantageously within 0.002 Angstrom, more advantageously within 0.001 Angstrom. By use of a solid solution of two or more garnets, e.g., two congruent garnet compositions, an acceptable lattice parameter is able to be attained. In another aspect, the substrate is a single crystal material consisting essentially of a solid solution of gadolinium scandium gallium garnet and gadolinium scandium aluminum garnet, or a solid solution of gadolinium scandium gallium garnet and terbium scandium gallium garnet. These combinations, in proper compositional ratios, are able to provide lattice parameters that facilitate formation of desirable, high-Eu magneto-optic garnets.
Garnets of the above formula in which x is 1 tend to provide highly desirable magnetic properties. Inclusion of aluminum is useful in some cases, however, because even a small amount of aluminum can modify the lattice parameter to an extent that widens the range of potential substrate materials.
REFERENCES:
patent: 5303256 (1994-04-01), Sumida
patent: 5608570 (1997-03-01), Brandle, Jr. et al.
patent: 5801875 (1998-09-01), Brandle, Jr. et al.
V.J. Fratello, et al “Nucleation Induced Coercivity In Faraday Rotator Garnets”, Proceedings of International Symposium on Laser and Nonlinear Optical Material, 1997, T. Sasaki, editor, pp. 59-66.
D. Mateika, et al “Lattice Parameters And Distribution Coefficients As Function OF Ca, Mg And Zr concentrations In Czochralski Grown Rare Earth Gallium Garnets”, Journal of Crystal Growth, vol. 56, pp. 677-689, Jul. 22, 1981.
V.J. Fratello, et al Innovative Improvements In Bismuth-Doped Rare-Earth Iron Garnet Faraday Rotators, IEEE Transactions On Magnetics, vol 32, No. 5, pp. 4102-4107, Sep. 1996.
V.J. Fratello, et al “Epitaxial Garnet Films for Nonreciprocal Magneto-Optic Devices”, Handbook of Thin Film Devices, vol. 4: Magnetic Thin Fil Devices, ed. M.H. Francombe, Academic Press, pp. 93-141.
V.J. Fratello, et al Journal of Applied Physics, vol. 60, pp718-720, Jul. 15, 1986.
edited by W.H. von Aulock, “Handbook of Microwave Ferrite Materials”, Academic Press 1965 pp. 70-73, 86, 153, 163, 174.
edited by A. Paoletti, “Physics of Magnetic Garnets”, North Holland, 1978, pp. 9-22; and J. Smit and H.P.J. Wijn, 1959, pp. 212-215.
P. Hansen et al, Landolt-Bornstein New Series, Group III, vol. 12, Part A, Springer-Verlag, 1978, pp. 22-23.
W.P. Wolf, Phys. Rev., vol. 118, p. 1490 (1960).
V.J. Fratello et al, “Growth of Single-Crystal . . . ”, Reprinted from Journal of Crystal Growth, vol. 75, pp. 281-283, North-Holland, Amsterdam, Jan. 16, 1986.
V.J. Fratello et al, “Growth of Congruently Melting Gadolinium Scandium Gallium Garnet”, Journal of Crystal Growth, vol. 80, pp 26-32, North-Holland, Amsterdam, (1987).
V.J. Fratello et al, “Effect of Bismuth Doping on Thermal Expansion and Misfit Dislocations in Epitaxial Iron Garnets”, Journal of Crystal Growth, vol. 142, pp. 93-102, (1994).
H.L. Huang, editor, Proceedings of the Fifth Symposium on Magnetism and Magnetic Materials, “Recent Advances in Magnetism and Magnetic Materials”, Taipei, Taiwan, Apr. 19-20, 1989.
C.D. Brandle et al, “Crystal Stoichiometry and Growth of Rare-Earth Garnets Containing Scandium”, vol. 20, Journal of Crystal Growth, pp. 1-5, (1973).
S. Yu. Zinov'ev, “Determination of Optimal Composition For Growth of Gadolinium-Scandium-Aluminum Garnet”, Plenum Publishing Corporation, (1990).
G.B. Lutts, “Crystals of Solid Solutions of Scandium-Containing Garnets For Solid-State Lasers”, Allerton Press, Inc. (1991).
Patent Abstracts of Japan, Pub. No. 2000119100, Apr. 25, 2000.
Brandle, Jr. Charles David
Fratello Vincent Jerome
Paget Kathleen M.
Subramanian Shanthi
Dickstein , Shapiro, Morin & Oshinsky, LLP
Hiteshew Felisa
TriQuint Technology Holding Co.
LandOfFree
Process for fabricating an article comprising a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for fabricating an article comprising a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for fabricating an article comprising a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3222381