We report the correlation between the crystalline structure, electronic structure and magnetic properties of Co2FeAl films as a function of growing temperature both experimentally and theoretically. The Co2FeAl film grown at room... more
We report the correlation between the crystalline structure, electronic structure and magnetic properties of Co2FeAl films as a function of growing temperature both experimentally and theoretically. The Co2FeAl film grown at room temperature is initially in the partially disordered B2 state, but then it gains a much higher ordered structure with increasing growing temperature due to its transition from short-range to long-range crystallographic order by surface diffusion. Electron energy loss spectroscopy measurements reveals that the increase in the I(L3)/I(L2) ratio of Co can be attributed to the enhanced ferromagnetic exchange interaction between neighboring Co atoms and the fact that the Co contribution is more dominant than the Fe contribution. As the growing temperature increases, many more unoccupied 3d states in Co are observed, hence the Gilbert damping constant increases due to a strong spin–orbit interaction. We also present the results of highly accurate quasiparticle self-consistent GW calculations and confirm that Co2FeAl in an ideal L21 structure is indeed a half-metal with a well-defined band gap in the minority spin channel.
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This paper describes the characteristics of a high resolution infrared IR imaging system operating over the wavelength range of 830–1100 nm, based on a modified 8 Mpixels commercial digital camera, with which nonspecialists can obtain IR... more
This paper describes the characteristics of a high resolution infrared IR imaging system operating over the wavelength range of 830–1100 nm, based on a modified 8 Mpixels commercial digital camera, with which nonspecialists can obtain IR reflectograms of works of art in situ in a museum environment. The relevant imaging properties of sensitivity, resolution, noise, and contrast are characterized and the capabilities of this system are illustrated with an example that has revealed important new information about the working practices of a 16th century artist. © 2009 American Institute of Physics. DOI: 10.1063/1.3174431
This paper describes the characteristics of a high resolution infrared IR imaging system operating over the wavelength range of 830–1100 nm, based on a modified 8 Mpixels commercial digital camera, with which nonspecialists can obtain IR... more
This paper describes the characteristics of a high resolution infrared IR imaging system operating over the wavelength range of 830–1100 nm, based on a modified 8 Mpixels commercial digital camera, with which nonspecialists can obtain IR reflectograms of works of art in situ in a museum environment. The relevant imaging properties of sensitivity, resolution, noise, and contrast are characterized and the capabilities of this system are illustrated with an example that has revealed important new information about the working practices of a 16th century artist. © 2009 American Institute of Physics. DOI: 10.1063/1.3174431
We report the fabrication of a superlattice consisting of alternating single atomic planes of Mo and Ta. This is the first metallic superlattice fabricated with monolayer modulation. This superlattice is the lower limit of a set of... more
We report the fabrication of a superlattice consisting of alternating single atomic planes of Mo and Ta. This is the first metallic superlattice fabricated with monolayer modulation. This superlattice is the lower limit of a set of superlattices with wavelengths modulated by integer numbers of atomic planes of Mo and Ta. These superlattices retain structural coherence and exhibit metallic resistivity
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We report the fabrication of a superlattice consisting of alternating single atomic planes of Mo and Ta. This is the first metallic superlattice fabricated with monolayer modulation. This superlattice is the lower limit of a set of... more
We report the fabrication of a superlattice consisting of alternating single atomic planes of Mo and Ta. This is the first metallic superlattice fabricated with monolayer modulation. This superlattice is the lower limit of a set of superlattices with wavelengths modulated by integer numbers of atomic planes of Mo and Ta. These superlattices retain structural coherence and exhibit metallic resistivity
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The preparation by sputtering of artificial metallic superlattices is described, as are the results of x-ray structural determinations. Tunneling and resistivity measurements on these materials are reported.
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The preparation by sputtering of artificial metallic superlattices is described, as are the results of x-ray structural determinations. Tunneling and resistivity measurements on these materials are reported.
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Since the coherence length is of order 50 A to 1 m, it is possible to alternately layer thin films of a superconductor with another material to affect the physical properties of the resulting superlattice. A brief description of our... more
Since the coherence length is of order 50 A to 1 m, it is possible to alternately layer thin films of a superconductor with another material to affect the physical properties of the resulting superlattice. A brief description of our sputtering technique used to prepare superlattices consisting of Nb/Cu and Ta/Mo is given. Optical interferometry, x-ray diffraction and ion beam analysis techniques independently confirm that control of +-0.3% is achieved over the amount of material deposited in each layer. Results of a study of Josephson tunneling to Nb/Cu metallic superlattices are reviewed. These measurements enable a determination of the London penetration depth to be made as a function of superlattice layer thickness.
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Since the coherence length is of order 50 A to 1 m, it is possible to alternately layer thin films of a superconductor with another material to affect the physical properties of the resulting superlattice. A brief description of our... more
Since the coherence length is of order 50 A to 1 m, it is possible to alternately layer thin films of a superconductor with another material to affect the physical properties of the resulting superlattice. A brief description of our sputtering technique used to prepare superlattices consisting of Nb/Cu and Ta/Mo is given. Optical interferometry, x-ray diffraction and ion beam analysis techniques independently confirm that control of +-0.3% is achieved over the amount of material deposited in each layer. Results of a study of Josephson tunneling to Nb/Cu metallic superlattices are reviewed. These measurements enable a determination of the London penetration depth to be made as a function of superlattice layer thickness.
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Recent interest in the magnetic and magneto-optic properties of transition metal/ transition metal multilayers has been stimulated by the discovery of perpendicular magnetism in particular systems.1,2 However, partially due to the large... more
Recent interest in the magnetic and magneto-optic properties of transition metal/ transition metal multilayers has been stimulated by the discovery of perpendicular magnetism in particular systems.1,2 However, partially due to the large variety of thin-film deposition methods and growth conditions, it has been difficult to obtain a clear understanding of the mechanisms of interfacial magnetic anisotropy. In order to create controlled and well characterized interfaces, we have grown a series of epitaxial Co/Pd superlattices on single-crystal GaAs(110) substrates by Molecular Beam Epitaxy (MBE). This paper describes the growth procedure, structural characterization, and the magnetic and magneto-optic properties of these superlattices. Comparisons are made to a series of non-epitaxial, polycrystalline multilayers that were simultaneously deposited on Si substrates.
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Recent interest in the magnetic and magneto-optic properties of transition metal/ transition metal multilayers has been stimulated by the discovery of perpendicular magnetism in particular systems.1,2 However, partially due to the large... more
Recent interest in the magnetic and magneto-optic properties of transition metal/ transition metal multilayers has been stimulated by the discovery of perpendicular magnetism in particular systems.1,2 However, partially due to the large variety of thin-film deposition methods and growth conditions, it has been difficult to obtain a clear understanding of the mechanisms of interfacial magnetic anisotropy. In order to create controlled and well characterized interfaces, we have grown a series of epitaxial Co/Pd superlattices on single-crystal GaAs(110) substrates by Molecular Beam Epitaxy (MBE). This paper describes the growth procedure, structural characterization, and the magnetic and magneto-optic properties of these superlattices. Comparisons are made to a series of non-epitaxial, polycrystalline multilayers that were simultaneously deposited on Si substrates.
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Abstract We review our recent results on the superconducting properties of artificially prepared metallic heterostructures. Our sputtering system used to prepare these materials is described in detail along with a calculation of the... more
Abstract We review our recent results on the superconducting properties of artificially prepared metallic heterostructures. Our sputtering system used to prepare these materials is described in detail along with a calculation of the thermalization of sputtered atoms. The structure of Nb/Cu and Nb/Ti heterostructures is discussed, as are Tc, energy gap, and phonon frequency measurements.
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Abstract We review our recent results on the superconducting properties of artificially prepared metallic heterostructures. Our sputtering system used to prepare these materials is described in detail along with a calculation of the... more
Abstract We review our recent results on the superconducting properties of artificially prepared metallic heterostructures. Our sputtering system used to prepare these materials is described in detail along with a calculation of the thermalization of sputtered atoms. The structure of Nb/Cu and Nb/Ti heterostructures is discussed, as are Tc, energy gap, and phonon frequency measurements.
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We grew superlattices of Mo and Ta on sapphire substrates using magnetically enhanced de triode sputtering, where a rotating substrate table alternately passes over the targets to create multilayers. Microprocessor control of the... more
We grew superlattices of Mo and Ta on sapphire substrates using magnetically enhanced de triode sputtering, where a rotating substrate table alternately passes over the targets to create multilayers. Microprocessor control of the sputtering process allowed us to keep layer thicknesses constant to ±0.3%. The wavelengths were modulated by an integer number, n, of atomic planes of Mo and Ta, where n ranged from a value of 153 (λ = 700 A) to the monolayer limit of 1 (λ = 4.57 A).
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Tunneling studies of artificially prepared Nb-Cu superlattices have been performed. Individual layers were in the range 8-5000 Å with total sample thicknesses∼ 1 μm. The coupling strength 2 Δ/k T c shows a continuous decrease from values... more
Tunneling studies of artificially prepared Nb-Cu superlattices have been performed. Individual layers were in the range 8-5000 Å with total sample thicknesses∼ 1 μm. The coupling strength 2 Δ/k T c shows a continuous decrease from values of∼ 3.8 (thick layers ...
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Research Interests:
Members of the R2Fe3Si5 series become either superconducting or magnetically ordered depending on whether the metal atom R (= rare earth, Y or Sc) is diamagnetic or paramagnetic respectively. Moessbauer effect and magnetization... more
Members of the R2Fe3Si5 series become either superconducting or magnetically ordered depending on whether the metal atom R (= rare earth, Y or Sc) is diamagnetic or paramagnetic respectively. Moessbauer effect and magnetization measurements were made to determine the magnetic state of the iron and the nature of the superconducting electrons. Iron 57 Moessbauer measurements on the Sc, Dy and Er compounds all showed two partially resolved, quadrupole split spectra at all temperatures from 300 to 1.5 K, indicating that there is no resolvable magnetic interaction at the iron site. The nature of the superconducting electrons in the series is discussed in the light of available measurements.
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Research Interests: Phase Diagrams, Mathematical Sciences, Dynamical mean field theory, Mott metal-insulator transition, Anderson Model, and 14 morePhysical sciences, Randomness, Magnetic Properties, Proximity Effect, Pseudogap, Electronic Structure, Bose Hubbard Model, Anderson localization, Spin Glass, Mott Transition, Three Dimensional, Fermi Level, Fermionic Hubbard Model, and Mean Field Approximation
Members of the R2Fe3Si5 series become either superconducting or magnetically ordered depending on whether the metal atom R( = rare earth, Y or Sc) is diamagnetic or paramagnetic respectively. We have taken Mo¨ssbauer effect and... more
Members of the R2Fe3Si5 series become either superconducting or magnetically ordered depending on whether the metal atom R( = rare earth, Y or Sc) is diamagnetic or paramagnetic respectively. We have taken Mo¨ssbauer effect and magnetization measurements to determine the magnetic state of the iron and the nature of the superconducting electrons. 57Fe Mo¨ssbauer measurements on the Sc, Dy and
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Effect of transition‐metal overlayers on the perpendicular magnetism of MBE‐grown, ultra‐thin Co films. [Journal of Applied Physics 73, 6192 (1993)]. Brad N. Engel, Michael H. Wiedmann, Robert A. Van Leeuwen, Charles M. Falco. Abstract. ...
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We have grown epitaxial superconductor/spin‐glass multilayers, Nb/CuMn, as well as complimentary nonmagnetic Nb/Cu multilayers by molecular beam epitaxy. To probe the interaction of superconductivity and magnetism, we measured the... more
We have grown epitaxial superconductor/spin‐glass multilayers, Nb/CuMn, as well as complimentary nonmagnetic Nb/Cu multilayers by molecular beam epitaxy. To probe the interaction of superconductivity and magnetism, we measured the resistivity and ac susceptibility as a function of temperature for multilayers of nominally constant Nb thickness and varying normal‐metal thickness. The reduction of the transition temperature of the Nb/Cu multilayers with increasing Cu thickness is in excellent agreement with the de Gennes–Werthamer proximity effect theory. The inclusion of Mn in the Cu causes a significant additional suppression of the transition temperatures relative to the Nb/Cu multilayers. The extension of the de Gennes–Werthamer theory to include the effects of random magnetic impurities agrees well with the data from the Nb/CuMn multilayers for small CuMn layer thicknesses. However, deviations occur at the largest CuMn thicknesses studied. These deviations between the data and theory may be due to a dec...
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We observe a systematic increase in interface perpendicular magnetic anisotropy (PMA) with increasing Au-interlayer thickness tAu ranging from 1 to 5 monolayers (MLs) in Cu/Co/Au/Cu(111), where misfit strain in Co due to the epitaxial... more
We observe a systematic increase in interface perpendicular magnetic anisotropy (PMA) with increasing Au-interlayer thickness tAu ranging from 1 to 5 monolayers (MLs) in Cu/Co/Au/Cu(111), where misfit strain in Co due to the epitaxial growth increases with increasing tAu. This result can be understood within the framework of the magneto-elastic contribution to the interface PMA. With a Cu overlayer, a constant contribution of interface PMA as well as of volume anisotropy is observed when the Co thicknesses are greater than 1.3 ML. However, we have found an unexpected suppression of this variation of interface PMA with the use of Au overlayers instead of Cu ones. With Au or Pd overlayers, the PMA starts to degrade as the Co thickness is reduced below 2.5 ML.
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Several metallic superlattice systems were prepared by sputtering techniques, structurally characterized by X-ray diffraction (both Bragg and Laue), and measurements made of their electrical transport properties. These metallic systems... more
Several metallic superlattice systems were prepared by sputtering techniques, structurally characterized by X-ray diffraction (both Bragg and Laue), and measurements made of their electrical transport properties. These metallic systems are found to grow with excellent structural coherence perpendicular to the layers, as evidenced by a large number of superlattice lines in the X-ray diffraction spectra. Also described are additions made to equipment and facilities. The sputtering system has microprocessor control of the substrate rotation, as well as of the sputtering rate. With these microprocessors, it is possible to control the thickness of each layer of the superlattices to + or - 0.1%.
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Research Interests: Mechanical Engineering, Materials Science, Optics, Medical Imaging, Fiber Optics, and 15 moreTelecommunications, Photonics, Medicine, X Rays, Society, Ultraviolet, Applied, Optical, Thin Film, Light, Applied Optics, Optical physics, Soft X Ray, Extreme Ultraviolet, and Electrical And Electronic Engineering
... Rev. B27, 7186-7193 (1983). [9] P. Bisanti, MB Brodsky, GP Felcher, M. Grimsditch, and LR Sill, Surface waves in Au/Cr superlattices, Phys. Rev. ... John R. Dutcher, Sukmock Lee, Jeha Kim, John A. Bell, George I. Stegeman and Charles... more
... Rev. B27, 7186-7193 (1983). [9] P. Bisanti, MB Brodsky, GP Felcher, M. Grimsditch, and LR Sill, Surface waves in Au/Cr superlattices, Phys. Rev. ... John R. Dutcher, Sukmock Lee, Jeha Kim, John A. Bell, George I. Stegeman and Charles M. Falco, J. of Materials Sci. and Eng. ...
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Research Interests:
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Recently, renowned artist David Hockney observed that certain drawings and paintings from as early as the Renaissance seemed almost ``photographic'' in detail. Following an extensive visual investigation of western art of the past... more
Recently, renowned artist David Hockney observed that certain drawings and paintings from as early as the Renaissance seemed almost ``photographic'' in detail. Following an extensive visual investigation of western art of the past 1000 years, he made the revolutionary claim that artists even of the prominence of van Eyck and Bellini must have used optical aids. However, many art historians
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Mo/Ta superlattices with superlattice wavelengths in the range 20-180 A were made by alternately sputtering these components. The results of a variety of X-ray diffraction studies used to structurally characterize these samples are... more
Mo/Ta superlattices with superlattice wavelengths in the range 20-180 A were made by alternately sputtering these components. The results of a variety of X-ray diffraction studies used to structurally characterize these samples are reported.
Research Interests: Engineering, Condensed Matter Physics, Materials Science, Applied Physics, Control Systems, and 19 moreControl system, Crystal structure, Computers, Electronic Circuits, Mathematical Sciences, Elements, Thin Film, Physical sciences, Feedback Control, Fabrication, Diffraction, Sputtering, Magnetron, Superlattice, Elastic Scattering, X ray diffraction, Scattering, Crystalline Structure, and Superlattices
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ABSTRACT Powder CsI crystal has been deposited with vacuum thermal evaporation on three different kinds of substrates: Si, SiO2/Si and Pt/Si. We have analyzed and observed these CsI films with different depth and various preparation... more
ABSTRACT Powder CsI crystal has been deposited with vacuum thermal evaporation on three different kinds of substrates: Si, SiO2/Si and Pt/Si. We have analyzed and observed these CsI films with different depth and various preparation conditions by XRD measurement. Through analyzing, we find that in such process condition the crystal state of CsI film has a strong relationship with the crystal structure of substrate, and non-crystal substrate goes against crystallization. By contrasting standard XRD diagram of CsI(Tl), we discover that with the influence of the surface structure of substrate, CsI crystal film has a preferred orientation in (200) crystal face. We also notice that the preferred orientation of CsI film has a close relation with the depth of the film: the preferred orientation has been weakened as the depth of film turning from 70mum to 100mum.
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We report the growth, by molecular beam epitaxy, and superconducting behavior of Nb(110)/Pd(111) superlattices. The samples were grown on Cu(111) buffer layers which were grown on Si(111) wafers. Thick films of pure Nb(110) and Pd(111)... more
We report the growth, by molecular beam epitaxy, and superconducting behavior of Nb(110)/Pd(111) superlattices. The samples were grown on Cu(111) buffer layers which were grown on Si(111) wafers. Thick films of pure Nb(110) and Pd(111) were grown in the same way and used to measure the electron mean free paths and the superconducting transition temperature Tc of the Nb. Reflection high energy electron diffraction, low-angle x-ray reflectance, and high-angle x-ray diffraction confirm the good crystal structure and morphology of the samples. The thick films exhibit high residual resistivity ratios and Tc of the thick Nb film is not depressed from the bulk value as in typical polycrystalline thin films. The behavior of Tc as a function of Pd layer thickness is in agreement with the deGennes-Werthamer proximity effect theory, showing that Nb/Pd is a conventional proximity system. The effect of adding small amounts of Mn to the Pd will also be discussed. * Supported by the Office of Naval Research under contract N00014-92-J-1159.
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We have used spin-wave Brillouin scattering to study the perpendicular magnetic anisotropy of ultrathin Co/Au/Cu(111) films with various thicknesses of Au underlayer. From the field dependence of the spin-wave frequency we find that the... more
We have used spin-wave Brillouin scattering to study the perpendicular magnetic anisotropy of ultrathin Co/Au/Cu(111) films with various thicknesses of Au underlayer. From the field dependence of the spin-wave frequency we find that the second-order (fourth power) uniaxial perpendicular anisotropy increases monotonically with increasing Au-underlayer thickness ranging from 0 to 5 monolayers (ML), while the first-order (second power) anisotropy shows