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Full-Text Articles in Physics

Search For Radiative B,-Hadron Decays In Pp̅ Collisions At √S=1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Dec 2002

Search For Radiative B,-Hadron Decays In Pp̅ Collisions At √S=1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We have performed a search for radiative b-hadron decays using events produced in pp̅ collisions at √s=1.8 TeV and collected by the Collider Detector at Fermilab. The decays we considered were d0K*0(→K-π+) γ, s0→φ(→K+K-) γ, Λb0→ Λ(→pπ-) γ, and their charge conjugates. Two independent methods to identify photons from such decays were employed. In the first method, the photon was detected in the electromagnetic calorimeter. In the second method, the photon was identified by an electron-positron pair produced through the external photon ...


Limits On Extra Dimensions And New Particle Production In The Exclusive Photon, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Dec 2002

Limits On Extra Dimensions And New Particle Production In The Exclusive Photon, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

The exclusive γE/T signal has a small standard model cross section and is thus a channel sensitive to new physics. This signature is predicted by models with a superlight gravitino or with large extra spatial dimensions. We search for such signals at the Collider Detector at Fermilab, using 87   pb-1 of data at √s=1.8   TeV, and extract 95% C.L. limits on these processes. A limit of 221 GeV is set on the scale |F|1/2 in supersymmetric models. For 4, 6, and 8 extra dimensions, model-dependent limits on the fundamental mass scale MD ...


Perturbative Calculation Of The Triply Differential Cross Section For Photo-Double-Ionization Of He, Andrei Y. Istomin, N. L. Manakov, Anthony F. Starace Dec 2002

Perturbative Calculation Of The Triply Differential Cross Section For Photo-Double-Ionization Of He, Andrei Y. Istomin, N. L. Manakov, Anthony F. Starace

Anthony F. Starace Publications

Single-photon, two-electron ionization of He is analyzed, taking into account electron correlation using lowest-order perturbation theory and including all individual electron angular momenta in the final two-electron continuum. Perturbative account of electron correlation in the final state, which describes the so-called TS-1 mechanism of double photoionization, combined with a variational account of electron screening, is found to provide results for the triply differential cross section at an excess energy of 20 eV that are in excellent agreement with both absolute experimental data and results of non-perturbative calculations, for all kinematics of the process in which the TS-1 mechanism is expected ...


Search For The Production Of Single Sleptons Through R-Parity Violation In Pp̅ Collisions At √S = 1.8 Tev, V. M. Abazov, Gregory R. Snow, D0 Collaboration Dec 2002

Search For The Production Of Single Sleptons Through R-Parity Violation In Pp̅ Collisions At √S = 1.8 Tev, V. M. Abazov, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We report the first search for supersymmetric particles via s-channel production and decay of smuons or muon sneutrinos at hadronic colliders. The data for the two-muon and two-jets final states were collected by the D0 experiment and correspond to an integrated luminosity of 94 ± 5 pb-1. Assuming that R parity is violated via the single coupling λ′211, the number of candidate events is in agreement with expectation from the standard model. Exclusion contours are given in the (m0; m½) and (mΧ̅,mν planes for λ′211= 0.09, 0.08, and 0.07.


Two-Photon Bremsstrahlung Processes In Atoms: Polarization Effects And Analytic Results For The Coulomb Potential, A. A. Krylovetskiĭ, N. L. Manakov, S. I. Marmo, Anthony F. Starace Dec 2002

Two-Photon Bremsstrahlung Processes In Atoms: Polarization Effects And Analytic Results For The Coulomb Potential, A. A. Krylovetskiĭ, N. L. Manakov, S. I. Marmo, Anthony F. Starace

Anthony F. Starace Publications

The partial wave analysis of two-photon free–free (bremsstrahlung) electron transition cross sections during scattering by a static potential U(r), as well as by an atom with a nonzero angular momentum, is carried out. The dipole interaction with radiation is taken into account in the second order of perturbation theory for the general case of elliptic polarization of photons. The polarization and angular dependences of the twophoton potential scattering amplitude is presented as a combination of the scalar product of electron momenta and photon polarization vectors and five atomic parameters containing Legendre polynomials of the scattering angle as well ...


Search For Minimal Supergravity In Single-Electron Events With Jets And Large Missing Transverse Energy In Pp̅ Collisions At √S =1.8 Tev, V. M. Abazov, Gregory R. Snow, D0 Collaboration Dec 2002

Search For Minimal Supergravity In Single-Electron Events With Jets And Large Missing Transverse Energy In Pp̅ Collisions At √S =1.8 Tev, V. M. Abazov, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We describe a search for evidence of minimal supergravity (MSUGRA) in 92.7 pb-1 of data collected with the DØ detector at the Fermilab Tevatron pp̅ collider at√s =1.8 TeV. Events with a single electron, four or more jets, and large missing transverse energy were used in this search. The major backgrounds are from W +jets, misidentified multijet, tt̅, and WW production. We observe no excess above the expected number of background events in our data. A new limit in terms of MSUGRA model parameters is obtained.


Electronic-Structure Modifications Induced By Surface Segregation In La0.65Pb0.35Mno3 Thin Films, C.N. Borca, B. Xu, T. Komesu, H.-K. Jeong, M.T. Liu, Sy_Hwang Liou, Shane Stadler, Y. Idzerda, Peter A. Dowben Dec 2002

Electronic-Structure Modifications Induced By Surface Segregation In La0.65Pb0.35Mno3 Thin Films, C.N. Borca, B. Xu, T. Komesu, H.-K. Jeong, M.T. Liu, Sy_Hwang Liou, Shane Stadler, Y. Idzerda, Peter A. Dowben

Peter Dowben Publications

Using spin-polarized inverse photoemission and X-ray absorption spectroscopy techniques, we show that the electronic structure of La0.65Pb0.35MnO3 thin films depends on the composition at the surface. With a gentle annealing procedure, the surface provides a maximum of 80% spin asymmetry at 0.5 eV above the Fermi level in spite of extensive Pb segregation. A heavily annealed (restructured) surface exhibits a reduced surface "ordering" temperature of 240 K (compared to the approximately 335 K bulk value) as well as a reduced spin asymmetry value of 40% at 0.5 eV above Fermi energy.


Coexistence Of Ferromagnetic And Glassy States In Mechanically Milled Gdal2, C. Stark, P. M. Shand, T. M. Pekarek, D. Williams, R. Brown, Lanping Yue, Diandra Leslie-Pelecky Dec 2002

Coexistence Of Ferromagnetic And Glassy States In Mechanically Milled Gdal2, C. Stark, P. M. Shand, T. M. Pekarek, D. Williams, R. Brown, Lanping Yue, Diandra Leslie-Pelecky

Diandra Leslie-Pelecky Publications

Measurements of DC susceptibility, AC susceptibility, and AC susceptibility with an applied DC bias field were performed on mechanically milled GdAl2. A paramagnetic phase exists above a temperature T ≈ 140 K. However, there are significant deviations from the Curie-Weiss Law in this temperature regime, suggesting multiple magnetic components. Fits to the high temperature data show that two Curie-Weiss terms represent the data quite well. Below 140 K one of these magnetic components becomes ferromagnetic as indicated by a shoulder in the AC susceptibility and DC susceptibility data. This ferromagnetic component is suppressed by the application of sufficiently strong DC ...


Effects Of Germanium On The Electronic Transport Mechanism In Co20 (Cu-XGeX)80 Nanogranular Ribbons, J. He, Z. D. Zhang, J. Ping Liu, David J. Sellmyer Dec 2002

Effects Of Germanium On The Electronic Transport Mechanism In Co20 (Cu-XGeX)80 Nanogranular Ribbons, J. He, Z. D. Zhang, J. Ping Liu, David J. Sellmyer

David Sellmyer Publications

The dependency of giant magnetoresistance (GMR) on the nonmagnetic matrix in nanogranular Co20 (Cu1-xGex)80 ribbons was studied. When the matrix Cu is substituted with semiconductor Ge, the magnetoresistance transitioned from negative to positive at low temperatures. The positive GMR effect is closely related to the quantity of Co/Co3Ge2/Co junctionlike configurations. This result provides evidence for the competition between two types of electronic transport mechanisms in the magnetic granular ribbons: (i) electronic spin-dependent scattering, inducing a negative magnetoresistance and (ii) Coulomb blockade of the electronic tunneling, inducing a positive magnetoresistance.


Cross Section For Forward J/Ψ Production In Pp̅ Collisions At √S=1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Nov 2002

Cross Section For Forward J/Ψ Production In Pp̅ Collisions At √S=1.8 Tev, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

The inclusive cross section for J/ψ production times the branching ratio B(J/ψ→μ+μ-) has been measured in the forward pseudorapidity region: B×dσ[+p→J/ψ(pT>10 GeV/c,2.1<|η|<2.6)+X]/dη=192±9(stat)±29(syst) pb. The results are based on 74.1±5.2 pb-1 of data collected by the CDF Collaboration at the Fermilab Tevatron Collider. The measurements extend earlier measurements of the D0 Collaboration to higher pTJ/ψ. In the kinematic range where the experiments partially overlap, these data are in good agreement with previous measurements.


Heterojunction Diode Fabrication From Polyaniline And A Ferroelectric Polymer, B Xu, Y. Ovchenkov, Mengjun Bai, A. N. Caruso, A.V. Sorokin, Stephen Ducharme, Bermard Doudin, Peter A. Dowben Nov 2002

Heterojunction Diode Fabrication From Polyaniline And A Ferroelectric Polymer, B Xu, Y. Ovchenkov, Mengjun Bai, A. N. Caruso, A.V. Sorokin, Stephen Ducharme, Bermard Doudin, Peter A. Dowben

Peter Dowben Publications

We have fabricated a p – n heterojunction diode by vapor depositing a thin film of polyaniline on top of the crystalline copolymer: poly(vinylidene fluoride with trifluoroethylene). The formation of a diode is expected from the band offsets of the two polymers near the Fermi level. The interface between the two components was investigated, and an abrupt interface was found that is very different from the inorganic analog.


Study Of Energetic Ion Generation From High-Intensity-Laser Dense-Plasma Interactions, K. Flippo, Anatoly Maksimchuk, Sudeep Banerjee, K. Nash, V. Wong, T. Lin, K. Nemoto, V. Yu. Bychenkov, Y. Sentoku, G. Mourou, Donald P. Umstadter Nov 2002

Study Of Energetic Ion Generation From High-Intensity-Laser Dense-Plasma Interactions, K. Flippo, Anatoly Maksimchuk, Sudeep Banerjee, K. Nash, V. Wong, T. Lin, K. Nemoto, V. Yu. Bychenkov, Y. Sentoku, G. Mourou, Donald P. Umstadter

Donald Umstadter Publications

We report on the characteristics of an ultrafast-laser driven proton beam from thinfilm targets. The difference in proton beam profiles, beam energies, and laser induced back ablation plumes between a dielectric (Mylar) and a conductor (aluminum) are discussed. Evidence for front-side acceleration and a method for beam manipulation are also presented.


A Proof-Of-Principle Experiment Of Optical Injection Of Electrons In Laser-Driven Plasma Waves, N. Saleh, P. Zhang, Shouyuan Chen, Z.-M. Sheng, Anatoly Maksimchuk, V. Yanovsky, Donald P. Umstadter Nov 2002

A Proof-Of-Principle Experiment Of Optical Injection Of Electrons In Laser-Driven Plasma Waves, N. Saleh, P. Zhang, Shouyuan Chen, Z.-M. Sheng, Anatoly Maksimchuk, V. Yanovsky, Donald P. Umstadter

Donald Umstadter Publications

We report on a proof-of-principle experiment that demonstrates, for the first time, the feasibility of optically injecting electrons into laser-driven plasma waves, first proposed by [D. Umstadter, J.-K. Kim, and E. Dodd, Phys. Rev. Lett. 76, 2073 (1996)l. Using a Table-Top-Tera Watt laser system (I ~5x1018 W/cm2, λ = 1 μm, τ = 400 fs), whose output beam is split by 1:4 ratio into a pump and injection beams, respectively, spatial (within 10 μm) and temporal (within 400 fs) overlap of the two beams were achieved by intersecting them orthogonally in an under-dense (~ 4x1019 cm ...


Developments In Relativistic Nonlinear Optics, Donald P. Umstadter, Sudeep Banerjee, Shouyuan Chen, E. Dodd, K. Flippo, Anatoly Maksimchuk, N. Saleh, A. Valenzuela, P. Zhang Nov 2002

Developments In Relativistic Nonlinear Optics, Donald P. Umstadter, Sudeep Banerjee, Shouyuan Chen, E. Dodd, K. Flippo, Anatoly Maksimchuk, N. Saleh, A. Valenzuela, P. Zhang

Donald Umstadter Publications

We report recent results of experiments and simulations in the regime of peak laser intensities above 1019 W/cm2, including the following topics: (1) electron and proton acceleration to energies in excess of 10 MeV in well collimated beams; (2) use of laser chirp to control the growth of plasma waves and acceleration of electrons by the Raman instability; (3) all optical injection and acceleration of electrons; (4) relativistic self-focusing by means of the mutual index of refraction of two overlapping laser pulses; (5) creation of a radioisotope by the reaction 10B(d,n)11C; (6 ...


Langmuir-Blodgett Films Of Polyethylene, A.V. Sorokin, Mengjun Bai, Stephen Ducharme, Matt Poulsen Nov 2002

Langmuir-Blodgett Films Of Polyethylene, A.V. Sorokin, Mengjun Bai, Stephen Ducharme, Matt Poulsen

Stephen Ducharme Publications

The possibility to obtain surface layers on water and prepare solid multilayer Langmuir–Blodgett films of medium-density polyethylene is shown. The polymer film on water is stable, demonstrates a reversible surface pressure-area isotherm up to 15 mN/m, and can be deposited onto a substrate using the Langmuir–Blodgett technique in a wide range of surface pressures. The thickness of a single deposited layer is 5.1 nm on average. The dielectric and optical constants of multilayer films are near their bulk values. The films exhibit high dielectric strength of at least 200 MV/m.


Magnetic Relaxation Phenomena In The Superspin-Glass System [Co80Fe20/Al2O3]10, Sarbeswar Sahoo, O. Petracic, Christian Binek, Wolfgang Kleemann, J. B. Sousa, Susana Cardoso De Freitas, P. P. Freitas Nov 2002

Magnetic Relaxation Phenomena In The Superspin-Glass System [Co80Fe20/Al2O3]10, Sarbeswar Sahoo, O. Petracic, Christian Binek, Wolfgang Kleemann, J. B. Sousa, Susana Cardoso De Freitas, P. P. Freitas

Christian Binek Publications

Relaxation and temperature cycles of thermoremanent magnetization, MTRM, in the superspin-glass phase of [Co80Fe20 (0.9 nm)/Al2O3 (3 nm)] 10 have been investigated. The relaxation of MTRM exhibits ageing phenomena. In negative temperature cycles for temperature steps larger than 1 K the magnetic state is retrieved (memory effect) on returning to the measurement temperature. This property is independent of the application of a field step during intermediate cooling. In positive temperature cycles the relaxation is suppressed after temporary heating. The observations are discussed in the light of both the droplet and ...


Curie Temperature Of Fept:B2O3 Nanocomposite Films, H. Zeng, Renat F. Sabirianov, O. Mryasov, M.L. Yan, K. Cho, David J. Sellmyer Nov 2002

Curie Temperature Of Fept:B2O3 Nanocomposite Films, H. Zeng, Renat F. Sabirianov, O. Mryasov, M.L. Yan, K. Cho, David J. Sellmyer

David Sellmyer Publications

We report results on experimental and theoretical studies of structural and magnetic properties of FePt: B2O3 nanocomposite films. It was found for films prepared by magnetron sputtering with subsequent annealing that lattice parameters a and c of fct FePt change with significantly different rates with increase of the B2O3 fraction. As a consequence, fundamental magnetic properties change markedly, with the Curie temperature decreasing by 36% for 25% FePt volume fraction compared with the bulk value. Using an ab initio parametrization of magnetic interactions, we propose statistical model of thermal fluctuations in fct FePt, which ...


Search For R-Parity Violating Supersymmetry In Two-Muon And Four-Jet Topologies, V. M. Abazov, Gregory R. Snow, D0 Collaboration Oct 2002

Search For R-Parity Violating Supersymmetry In Two-Muon And Four-Jet Topologies, V. M. Abazov, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

We present results of a search for R-parity-violating decay of the neutralino Χ̅10, taken as the lightest supersymmetric particle, to a muon and two jets. The decay proceeds through a lepton-number violating coupling λ2jk1 (j =1, 2; k = 1; 2, 3), with R-parity conservation in all other production and decay processes. In the absence of candidate events from 77.5 ± 3.9 pb-1 of data collected by the D0 experiment at the Fermilab Tevatron in pp̅ collisions at√s =1.8 TeV, and with an expected background of 0.18 ± 0.03 ...


Plateau Effects In The Spectra Of Electrons Scattered From Atoms In A Strong Laser Field, N. L. Manakov, Anthony F. Starace, A. V. Flegel, M. V. Frolov Oct 2002

Plateau Effects In The Spectra Of Electrons Scattered From Atoms In A Strong Laser Field, N. L. Manakov, Anthony F. Starace, A. V. Flegel, M. V. Frolov

Anthony F. Starace Publications

An exact quantum solution of the problem of electron scattering from a short-range potential in the presence of a strong elliptically polarized laser field is obtained. The differential scattering cross section as a function of the number of absorbed (or emitted) photons exhibits a plateau caused by the rescattering of electrons from the scattering center. Numerical results for a linearly polarized laser field are presented, and it is shown that the plateau boundaries agree well with classical estimates.


Phase Dependence Of Thomson Scattering In An Ultraintense Laser Field, Fei He, Y. Y. Lau, Donald P. Umstadter, Trevor Strickler Oct 2002

Phase Dependence Of Thomson Scattering In An Ultraintense Laser Field, Fei He, Y. Y. Lau, Donald P. Umstadter, Trevor Strickler

Donald Umstadter Publications

The Thomson scattering spectra of an electron by an ultraintense laser field are computed. It is found that the electron orbit, and therefore its nonlinear Thomson scattering spectra, depend critically on the amplitude of the ultraintense laser field and on the phase at which the electron sees the laser electric field. Contrary to some customary notions, the Thomson scattering spectra, in general, do not occur at integer multiples of the laser frequency and the maximum frequency is proportional to the first instead of the third power of the electric field strength for the case of an ultraintense laser. The implications ...


Training Of The Exchange-Bias Effect In Nio-Fe Heterostructures, A. Hochstrat, Christian Binek, Wolfgang Kleemann Sep 2002

Training Of The Exchange-Bias Effect In Nio-Fe Heterostructures, A. Hochstrat, Christian Binek, Wolfgang Kleemann

Christian Binek Publications

The training effect of a NiO(001)/Fe(110) heterostructure is studied from magnetic hysteresis loops measured by superconducting quantum interference device magnetometry. Consecutive hysteresis loops exhibit a decreasing exchange bias effect. This behavior is known as the training effect, which reflects the dependence of the exchange bias field on the antiferromagnetic interface magnetization. In order to evidence this dependence, we study the decrease of the total saturation magnetization of the heterostructure for an increasing number of hysteresis cycles. Assuming proportionality between the interface magnetization and the total saturation magnetization, the description of the data is consistent within the phenomenological ...


Domain Wall Relaxation, Creep, Sliding, And Switching In Superferromagnetic Discontinuous Co80Fe20/Al2O3 Multilayers, X. Chen, O. Sichelschmidt, Wolfgang Kleemann, Christian Binek, J.B. Sousa, Susana Cardoso De Freitas, P.P. Freitas Sep 2002

Domain Wall Relaxation, Creep, Sliding, And Switching In Superferromagnetic Discontinuous Co80Fe20/Al2O3 Multilayers, X. Chen, O. Sichelschmidt, Wolfgang Kleemann, Christian Binek, J.B. Sousa, Susana Cardoso De Freitas, P.P. Freitas

Christian Binek Publications

The ac susceptibility of a superferromagnetic discontinuous multilayer [Co80Fe20(1.4   nm)/ Al2O3(3   nm)]10 is measured as a function of temperature, frequency, and field amplitude and compared to static and dynamic hysteresis loops. Its properties are successfully mapped onto the predicted [T. Nattermann, V. Pokrovsky, and V. M. Vinokur, Phys. Rev. Lett. 87, 197005 (2001).] dynamical phase transitions, which link the relaxation, creep, sliding, and switching regimes of pinned domain walls.


Imaging And Engineering The Nanoscale-Domain Structure Of A Sr0.61Ba0.39Nb2O6 Crystal Using A Scanning Force Microscope, K. Terabe, S. Takekawa, M. Nakamura, K. Kitamura, Alexei Gruverman Sep 2002

Imaging And Engineering The Nanoscale-Domain Structure Of A Sr0.61Ba0.39Nb2O6 Crystal Using A Scanning Force Microscope, K. Terabe, S. Takekawa, M. Nakamura, K. Kitamura, Alexei Gruverman

Alexei Gruverman Publications

We have investigated the ferroelectric domain structure formed in a Sr0.61Ba0.39Nb2O6 single crystal by cooling the crystal through the Curie point. Imaging the etched surface structure using a scanning force microscope (SFM) in both the topographic mode and the piezoresponse mode revealed that a multidomain structure of nanoscale island-like domains was formed. The island-like domains could be inverted by applying an appropriate voltage using a conductive SFM tip. Furthermore, a nanoscale periodically inverted-domain structure was artificially fabricated using the crystal which underwent poling treatment.


Oxidation Of Metals At The Chromium Oxide Interface, Ruihua Cheng, C.N. Borca, N. Pilet, Bo Xu, Lu Yuan, Bernard Doudin, Sy_Hwang Liou, Peter A. Dowben Sep 2002

Oxidation Of Metals At The Chromium Oxide Interface, Ruihua Cheng, C.N. Borca, N. Pilet, Bo Xu, Lu Yuan, Bernard Doudin, Sy_Hwang Liou, Peter A. Dowben

Peter Dowben Publications

Metal thin-film deposition, over the Cr2O3 surface of CrO2 thin-film substrates, exhibits a redox reaction at the interface. The transition metal forms an oxide in combination with the reduction of the near-surface chromium oxide to Cr2O3 . The insulating barrier layer Cr2O3 increases with the formation of Pb3 O4 in Pb/Cr2O3 /CrO2 and CoO in Co/Cr2O3 /CrO2 junctions, respectively.


Branching Ratio Measurements Of Exclusive B+ Decays To Charmonium With The Collider Detector At Fermilab, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Sep 2002

Branching Ratio Measurements Of Exclusive B+ Decays To Charmonium With The Collider Detector At Fermilab, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report on measurements of the branching ratios of the decays B+→χc10 (1P)K+ and B+→J/ψK+π+π-, where χc10(1P)→J/ψγ and J/ψ→μ+μ- in pp̅ collisions at √s=1.8 TeV. Using a data sample from an integrated luminosity of 110 pb-1 collected by the Collider Detector at Fermilab we measure the branching ratios to be BR(B+→ χc10(1P)K+)=15.5±5.4(stat)±1.5(syst)±1.3(br)×10-4 and BR(B+→J/ψK+π ...


Permanent-Magnet Properties Of Thermally Processed Fept And Fept–Fe Multilayer Films, Jian Zhou, Ralph Skomski, Xingzhong Li, Wei Tang, George C. Hadjipanayis, David J. Sellmyer Sep 2002

Permanent-Magnet Properties Of Thermally Processed Fept And Fept–Fe Multilayer Films, Jian Zhou, Ralph Skomski, Xingzhong Li, Wei Tang, George C. Hadjipanayis, David J. Sellmyer

David Sellmyer Publications

FePt single-layer and FePt–Fe multilayer thin films are prepared by magnetron sputtering. By varying the Pt content, FePt, Fe3Pt, or a mixture of FePt and Fe3Pt can be obtained in Fe–Pt single layers. In annealed FePt–Fe multilayers, the coercivities decrease with the introduction of Fe layers compared to FePt single layers, while the magnetization increases. The single-phase behavior of the hysteresis loops of FePt–Fe multilayers indicates the existence of exchange coupling in these materials. For one FePt–Fe sample with optimized exchange coupling, the intrinsic properties correspond to an energy product of ...


Effect Of Grain Growth Inhibitors On The Hysteresis Properties Of Nd10Fe82C6B2Melt-Spun Alloys, M. Daniil, Y. Zhang, H. Okumura, George C. Hadjipanayis, David J. Sellmyer Sep 2002

Effect Of Grain Growth Inhibitors On The Hysteresis Properties Of Nd10Fe82C6B2Melt-Spun Alloys, M. Daniil, Y. Zhang, H. Okumura, George C. Hadjipanayis, David J. Sellmyer

David Sellmyer Publications

An effort has been made to improve the coercivity of nanocomposite Nd10Fe82C6B2 alloys, using small amounts (up to 1 at%) of Cr, Ti, Nb, Zr, and Ga. X-ray studies revealed that the amount of –Fe phase in both as-spun and annealed ribbons was significantly reduced for Nb and Zr substitutions, but increased for all the other substitutions. From the magnetic properties point of view, Zr (1 at%) was proven to be the most advantageous of all, since it increased the coercivity of annealed ribbons from 3.2 to 4.8 kOe and the ...


Nanoscale Observation Of Photo-Induced Domain Pinning And Investigation Of Imprint Behavior In Ferroelectric Thin Films, Alexei Gruverman, B. J. Rodriguez, R. J. Nemanich, A. I. Kingon Sep 2002

Nanoscale Observation Of Photo-Induced Domain Pinning And Investigation Of Imprint Behavior In Ferroelectric Thin Films, Alexei Gruverman, B. J. Rodriguez, R. J. Nemanich, A. I. Kingon

Alexei Gruverman Publications

Piezoresponse force microscopy has been used to investigate the nanoscale mechanism of imprint behavior of ferroelectric PbTiO3 thin films by studying the photoinduced changes in the hysteresis loops of individual grains. Illumination of the film with UV light resulted in a voltage shift opposite to that observed in ferroelectric thin film capacitors. This effect is attributed to the generation of an electric field within the surface dielectric layer as a result of the interaction between photo-induced charges and polarization charges. Application of a small non-switching bias to the film with simultaneous UV illumination resulted in domain pinning in the ...


Seedlayer And Preheating Effects On Crystallography And Recording Performance Of Cocrptb Perpendicular Media, Min Zheng, Geon Choe, Kenneth E. Johnson, Lan Gao, Sy_Hwang Liou Sep 2002

Seedlayer And Preheating Effects On Crystallography And Recording Performance Of Cocrptb Perpendicular Media, Min Zheng, Geon Choe, Kenneth E. Johnson, Lan Gao, Sy_Hwang Liou

Faculty Publications, Department of Physics and Astronomy

The effects of seedlayer (SL) and preheating on the crystallographic, magnetic, and recording properties of CoCr18Pt16B4 granular perpendicular magnetic media have been investigated. For the media with Ru as underlayer, although higher preheating improves both coercivity and squareness, the media is much noisier. With introducing Ta SL, Ru (0002)/Co (0002) crystallography is greatly enhanced. High coercivity, unity squareness, and negative nucleation field are achieved even at low preheating without degrading signal-to-noise ratio. In addition, the media is magnetically stable for a wide range of recording density.


Boron-Carbide And Boron Rich Rhobohedral Based Transistors And Tunnel Diodes, Peter A. Dowben Aug 2002

Boron-Carbide And Boron Rich Rhobohedral Based Transistors And Tunnel Diodes, Peter A. Dowben

Peter Dowben Publications

The present invention relates to the fabrication of a boron carbide/boron semiconductor devices. The results suggest that with respect to the approximately 2 eV band gap pure boron material, 0.9 eV band gap boron carbide (B5C) acts as a p-type material. Both boron and boron carbide (B5C) thin films were fabricated from single source borane cage molecules using plasma enhanced chemical vapor deposition (PECVD). Epitaxial growth does not appear to be a requirement. We have doped boron carbide grown by plasma enhanced chemical vapor deposition. The source gas close- 1,2-dicarbadecaborane (orthocarborane) was used ...