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- Keyword
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- FMR (16)
- BaFe₁₂O₁₉ (9)
- Microwave properties (8)
- Saturation magnetization (8)
- X-ray diffraction (5)
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- Barium hexaferrite (4)
- YBa₂Cu₃O₇₋ₓ (4)
- ATLAD (3)
- Al₂O₃ (3)
- BaM (3)
- Barium ferrite (3)
- Barium hexaferrite films (3)
- Epitaxial films (3)
- Ferromagnets (3)
- Magnetoelectric coupling (3)
- Resonance (3)
- Screen printed films (3)
- Anisotropy (2)
- BaFe₂O₄ (2)
- FeCoV (2)
- Ferrimagnetic barium hexaferrite (2)
- Ferrimagnetic resonance (2)
- Ferroelectrics (2)
- Ferromagnetism (2)
- Fe₂O₃ (2)
- Fluxoids (2)
- GGG substrates (2)
- GaAs substrates (2)
- High Tc (2)
- Hysteretic behavior (2)
Articles 31 - 60 of 92
Full-Text Articles in Electromagnetics and Photonics
Frequency-Dependence Of The Ferromagnetic-Resonance Linewidth Of Barium Ferrite, M. Elrayess, J. B. Sokoloff, C. Vittoria, W. Spurgeon
Frequency-Dependence Of The Ferromagnetic-Resonance Linewidth Of Barium Ferrite, M. Elrayess, J. B. Sokoloff, C. Vittoria, W. Spurgeon
Carmine Vittoria
Ferromagnetic resonance was measured in both a swept frequency mode of operation, in which the magnetic field was fixed, and a field swept mode, using field modulation techniques. Single-crystal spheres of 0.381, 0.305, and 0.483 mm in diameter were inserted in the waveguide and transmission was observed in the measurement. The g values for all the spheres averaged to 2.052 ± 0.011 and the uniaxial anisotropy field was 16.4 kOe. Our measurements show that the linewidth of barium ferrite is nearly independent of resonant frequency from 48 to 105 G Hz. This is in disagreement with the Kasuya-LeCraw two-magnon-one-phonon mechanism, …
Single Crystal Fe Films Grown On Ge(001) Substrates By Magnetron Sputtering, J. Lou, A. Daigle, L. Chen, Y. Q. Wu, V. G. Harris, C. Vittoria, N. X. Sun
Single Crystal Fe Films Grown On Ge(001) Substrates By Magnetron Sputtering, J. Lou, A. Daigle, L. Chen, Y. Q. Wu, V. G. Harris, C. Vittoria, N. X. Sun
Carmine Vittoria
Single crystal Fe films were grown on Ge (001) substrates by using dc magnetron sputtering. It was found that the microstructures and magnetic properties of Fe films on Ge substrates were strongly dependent upon the substrate temperature during the deposition process. There existed a narrow substrate temperature window of 125 ± 25°C for achieving single crystal Fe film on Ge. Lower substrate temperature led to polycrystalline Fe films due to limited mobility of Fe atoms, while higher substrate temperatures resulted in amorphous Fe-Ge alloy due to severe interdiffusion.
A Quantitative Model For The Nonlinear Response Of Fluxgate Magnetometers, A. L. Geiler, V. G. Harris, C. Vittoria, N. X. Sun
A Quantitative Model For The Nonlinear Response Of Fluxgate Magnetometers, A. L. Geiler, V. G. Harris, C. Vittoria, N. X. Sun
Carmine Vittoria
An analytical nonlinear hysteresis model was developed to describe the hysteresis loops of different magnetic materials, which was capable of fitting Permalloy films as an example. As a case study this model was applied in the sensitivity analysis of the fluxgate magnetometers where accurately capturing the nonlinear behavior of the magnetic core is crucial. Straightforward analytical equation of the output voltage signal as well as its harmonic decomposition was obtained for the fluxgate magnetometer as a function of hysteresis loop parameters. Sensitivity values predicted by the model were found to be consistent with the measured values published previously. The model …
Size Dependent Magnetic Properties And Cation Inversion In Chemically Synthesized Mnfe₂O₄ Nanoparticles, C. N. Chinnasamy, Aria Yang, S. D. Yoon, Kailin Hsu, M. D. Shultz, E. E. Carpenter, S. Mukerjee, C. Vittoria, V. G. Harris
Size Dependent Magnetic Properties And Cation Inversion In Chemically Synthesized Mnfe₂O₄ Nanoparticles, C. N. Chinnasamy, Aria Yang, S. D. Yoon, Kailin Hsu, M. D. Shultz, E. E. Carpenter, S. Mukerjee, C. Vittoria, V. G. Harris
Carmine Vittoria
MnFe₂O₄ nanoparticles with diameters ranging from about 4 to 50 nm were synthesized using a modified coprecipitation method. X-ray diffractograms revealed a pure phase spinel ferrite structure for all samples. Transmission electron microscopy showed that the particles consist of a mixture of both spherical (smaller) and cubic (larger) particles dictated by the reaction kinetics. The Néel temperatures (TN) of MnFe₂O₄ for various particle sizes were determined by using high temperature magnetometry. The ∽4 nm MnFe₂O₄ particles showed a TN of about 320°C whereas the ∽50 nm particles had a TN of about 400°C. The high Neel temperature, compared with the …
Observation Of Ultrahigh Critical Current Densities In High-Tc Superconducting Bridge Constrictions, H. Jiang, Y. Huang, H. How, S. Zhang, C. Vittoria, A. Widom, D. B. Chrisey, J. S. Horwitz, R. Lee
Observation Of Ultrahigh Critical Current Densities In High-Tc Superconducting Bridge Constrictions, H. Jiang, Y. Huang, H. How, S. Zhang, C. Vittoria, A. Widom, D. B. Chrisey, J. S. Horwitz, R. Lee
Carmine Vittoria
Narrow bridge structures were precisely fabricated (using novel ion-beam-milling techniques) on pulsed-laser-deposited YBa₂Cu₃O₇ films. The bridges have a length scale down to L ≃500 Å. Super-currents were observed to flow across the bridge structures with critical current densities up to Jc ≃1.3 x 109 A/cm², the highest critical current densities yet reported. The current-density magnitudes are consistent with the Onsager-Feynman vortex-ring-creation mechanism (for producing voltages across narrow constrictions) in the length scale region of ζ << L ≤Λ, with ζ the coherence length and Λ the London penetration depth. The highest Jc is in good agreement with the critical depairing mechanism.
Giant Magnetoelectric Coupling And E-Field Tunability In A Laminated Ni2mnga/Lead-Magnesium-Niobate-Lead Titanate Multiferroic Heterostructure, Yajie Chen, Jingmin Wang, Ming Liu, Jing Lou, Nian X. Sun, Carmine Vittoria, Vincent G. Harris
Giant Magnetoelectric Coupling And E-Field Tunability In A Laminated Ni2mnga/Lead-Magnesium-Niobate-Lead Titanate Multiferroic Heterostructure, Yajie Chen, Jingmin Wang, Ming Liu, Jing Lou, Nian X. Sun, Carmine Vittoria, Vincent G. Harris
Carmine Vittoria
The multiferroic properties of a laminated heterostructure consisting of magnetostrictive Ni2MnGa ribbon and piezoelectric lead-magnesium-niobate-lead titanate crystal are reported. A tunability of the electric field-induced magnetic field was measured by a shift in the ferromagnetic resonance (FMR) field by 230 Oe at X-band while applying an electric field of 6 kV/cm. Concomitantly, a frequency shift in the FMR of 370 MHz was observed. The sensitive tunability stems from a large linear magnetoelectric coupling coefficient, A=41 Oe cm/kV, measured in the heterostructure. This represents a new class of metallic multiferroic heterostructures that operate at microwave frequencies.
Effects Of Boron Addition To The Atomic Structure And Soft Magnetic Properties Of Fecob Films, Aria Yang, Hassan Imrane, Jing Lou, Johnny Kirkland, Carmine Vittoria, Nian Sun, Vincent G. Harris
Effects Of Boron Addition To The Atomic Structure And Soft Magnetic Properties Of Fecob Films, Aria Yang, Hassan Imrane, Jing Lou, Johnny Kirkland, Carmine Vittoria, Nian Sun, Vincent G. Harris
Carmine Vittoria
The magnetic, microwave, and the atomic structure properties of (Fe₀.₇Co₀.₃)1-xBx sputtered films on glass substrates were investigated. The addition of boron induced a decrease in coercivity and ferromagnetic resonance linewidth. The amorphous structure was formed at x ∽0.075. Extended x-ray absorption fine structure (EXAFS) of Fe and Co showed the reduced Fourier transform (FT) amplitude, and increased Debye-Waller factors as x was increased, indicating the increased disorder due to the thermal and structural displacements. Possible Fe-B bonding was observed with a reduced bond length, which indicates boron atoms' preference for staying in the interstitial sites in bcc unit cell.
Time Domain Analyses Of The Converse Magnetoelectric Effect In A Multiferroic Metallic Glass-Relaxor Ferroelectric Heterostructure, Yajie Chen, Anton L. Geiler, Trifon Fitchorov, Carmine Vittoria, V. G. Harris
Time Domain Analyses Of The Converse Magnetoelectric Effect In A Multiferroic Metallic Glass-Relaxor Ferroelectric Heterostructure, Yajie Chen, Anton L. Geiler, Trifon Fitchorov, Carmine Vittoria, V. G. Harris
Carmine Vittoria
The dynamic time domain response of the converse magnetoelectric effect in a multiferroic Metglas®/Pb(Mg1/3Nb2/3)O₃-PbTiO₃ (PMN-PT) heterostructure, under the application of a square waveform electric field excitation of 8 kV/cm at a frequency of 0.4 Hz, is reported. The relaxation behavior followed a stretched power-law function allowing the calculation of an intrinsic time constant. Aging behavior of magnetoelectric coupling was observed after polarization switching of 1000 cycles. These phenomena are predominantly attributed to the temporal response of polarization within the PMN-PT crystal. Results elucidate the dynamic properties of relaxor-based multiferroic heterostructures and importantly define operational constraints for low frequency device operation.
Low-Loss Barium Ferrite Quasi-Single-Crystals For Microwave Application, Yajie Chen, Anton L. Geiler, Taiyang Chen, Tomokazu Sakai, C. Vittoria, V. G. Harris
Low-Loss Barium Ferrite Quasi-Single-Crystals For Microwave Application, Yajie Chen, Anton L. Geiler, Taiyang Chen, Tomokazu Sakai, C. Vittoria, V. G. Harris
Carmine Vittoria
Barium hexaferrites (BaFe₁₂O₁₉) are especially useful for microwave/millimeter devices. Due to large ferromagnetic resonance (FMR) loss (linewidths > 2 kOe), traditional compacts of polycrystalline Ba ferrites indeed hinder the utilization of the materials for practical devices. The present experiment demonstrates that the quasi-single-crystal Ba ferrite disks can be fabricated by a single solid-state reaction technique without liquid phase participation, combining with a processing of alignment for the ferrite seed crystals. The ferrite bulks show a pure hexagonal Ba ferrite phase, an expected 4πMs of 4.48 kG, and coercivity of 10∽20 Oe along the c axis, similar to the results of a …
A Microstrip Tunable Negative Refractive Index Metamaterial And Phase Shifter, P. He, J. Gao, C. T. Marinis, P. V. Parimi, C. Vittoria, V. G. Harris
A Microstrip Tunable Negative Refractive Index Metamaterial And Phase Shifter, P. He, J. Gao, C. T. Marinis, P. V. Parimi, C. Vittoria, V. G. Harris
Carmine Vittoria
A tunable negative refractive index metamaterial and miniature phase shifter have been designed and fabricated in a microstrip configuration for applications in radio frequency integrated circuits. The metamaterial consists of plasmonic copper wires and yttrium iron garnet slabs having a low insertion loss of 5 dB at the center of the transmission band. The yttrium iron garnet material enables the magnetic field tuning of the negative refractive index in a dynamic frequency band from 7.0 to 11.0 GHz. The insertion phase can be tuned by 45 degrees continuously by varying the bias field from 3.8 to 4.6 kOe at 9.0 …
Theory Of Amplified Ferrimagnetic Echoes, H. How, C. Vittoria
Theory Of Amplified Ferrimagnetic Echoes, H. How, C. Vittoria
Carmine Vittoria
Amplification of echo signals in ordered magnetic materials was postulated by many authors in the middle sixties. However, theoretical estimates of amplification were invariably several orders of magnitude higher than observed in ferrimagnetic materials. We have reformulated the equation of motion to include the nonlocal dipole-dipole interaction to describe the dynamic response of an echo. Our estimates of amplification compare reasonably well with measured values.
Measurement Of Kappa In High Tc Superconductors, R. Karim, H. How, C. Vittoria, A. Widom
Measurement Of Kappa In High Tc Superconductors, R. Karim, H. How, C. Vittoria, A. Widom
Carmine Vittoria
The experimental magnetic-field derivative of the microwave absorption signal, obtained using electron paramagnetic resonance techniques, has a line shape that depends on the Ginzburg-Landau model parameter κ of the superconducting sample at a given temperature. The type-II superconducting equation of state can be utilized to describe the drop in the output microwave power derivative, from its maximum at H ≃Hc1 to its much lower values when H ≫Hc1, in order to estimate the values of κ. The technique also allows for the experimental determination of hysteretic behavior in B as a function of H.
Ac Hall Measurements On High-Tc Superconductors, H. How, C. Vittoria, A. Widom
Ac Hall Measurements On High-Tc Superconductors, H. How, C. Vittoria, A. Widom
Carmine Vittoria
Hall experiments are carried out normally in bulk materials where a dc current is applied perpendicular to a static magnetic field. Since the dc Hall coefficient is small for type-II superconductors at temperatures well below the transition temperature Tc, the possibility of measuring the Hall coefficient of the superconductor under ac conditions is explored. It is found that the ac Hall coefficient can be readily detected through the measurement of the reflected microwave beam, whose polarization has been rotated 90° away from the incident wave irradiating on the surface of a high-Tc superconducting material biased by a dc magnetic field.
Growth And Characterization Of Thick Oriented Barium Hexaferrite Films On Mgo (111) Substrates, S. A. Oliver, S. D. Yoon, I Kozulin, M. L. Chen, C. Vittoria
Growth And Characterization Of Thick Oriented Barium Hexaferrite Films On Mgo (111) Substrates, S. A. Oliver, S. D. Yoon, I Kozulin, M. L. Chen, C. Vittoria
Carmine Vittoria
Highly oriented films of BaFe₁₂O₁₉ have been deposited onto MgO (111) substrates by pulsed laser ablation deposition. In contrast to epitaxial BaFe₁₂O₁₉ films grown on Al₂O₃ (001) substrates, these films experience an in-plane biaxial compressive stress, and do not crack or delaminate to thicknesses of at least 28 μm. X-ray diffraction, magnetometry, torque magnetometry, and ferrimagnetic resonance results all indicate excellent c-axis orientation normal to the film plane, and magnetic properties comparable to bulk values. The thickness and properties of these films approach those required for applications in low-loss self-biased nonreciprocal microwave devices
Electrically Controlled Magnetization Switching In A Multiferroic Heterostructure, Yajie Chen, Trifon Fitchorov, Carmine Vittoria, V. G. Harris
Electrically Controlled Magnetization Switching In A Multiferroic Heterostructure, Yajie Chen, Trifon Fitchorov, Carmine Vittoria, V. G. Harris
Carmine Vittoria
A demonstration of magnetization reversal via the application of electric field across a multiferroic heterostructure, consisting of a FeCoV ribbon bonded to a lead magnesium niobate-lead titanate crystal, is presented. The magnetization switching occurs by an abrupt change in magnetization near ferromagnetic coercivity, coinciding with an electrical field-induced magnetic anisotropy field. Experiments reveal a converse magnetoelectric coupling of α=μ0 (dM/dE) = 1.6 x 10-7 s m-1 upon magnetization reversal in the strain-mediated heterostructure. The frequency dependence of magnetization switching is presented and explained within the framework of a relaxation model for the multiferroic heterostructure.
Out-Of-Plane Ferromagnetic-Resonance Study Of Magnetically Coupled Fe/Cr/Fe Films, S. A. Oliver, C. Vittoria, J. J. Krebs, P. Lubitz, G. A. Prinz
Out-Of-Plane Ferromagnetic-Resonance Study Of Magnetically Coupled Fe/Cr/Fe Films, S. A. Oliver, C. Vittoria, J. J. Krebs, P. Lubitz, G. A. Prinz
Carmine Vittoria
Magnetically coupled single-crystal Fe/Cr/Fe (001) sandwiches have been studied by the ferromagnetic resonance (FMR) techniques. Such films have been previously shown to be antiferromagnetically coupled for a chromium layer thickness range 12 Å< tcr < 25 Å by variable frequency ferromagnetic resonance measurements along principal crystallographic axes, and other techniques. These measurements have been extended to include oblique angle application of the applied magnetic field (H) between principal crystallographic axes in the film plane and the film normal. Measured films had tcr = 13, 16, 17, and 28 Å. Ferromagnetic resonance measurements were taken using a fixed frequency 9.5-GHz cavity. Resonances …
Functionalization Of Feco Alloy Nanoparticles With Highly Dielectric Amorphous Oxide Coatings, Q. Nguyen, C. N. Chinnasamy, S. D. Yoon, S. Sivasubramanian, T. Sakai, A. Baraskar, S. Mukerjee, C. Vittoria, V. G. Harris
Functionalization Of Feco Alloy Nanoparticles With Highly Dielectric Amorphous Oxide Coatings, Q. Nguyen, C. N. Chinnasamy, S. D. Yoon, S. Sivasubramanian, T. Sakai, A. Baraskar, S. Mukerjee, C. Vittoria, V. G. Harris
Carmine Vittoria
FeCo alloy nanoparticles have been prepared by using a two step modified polyol process using Fe(II) chloride and Co acetate tetrahydrate as Fe and Co metal precursors. Tetraethyl silicate, aluminum isopropoxide, and zirconium(IV) acetyl acetonate were used to make amorphous SiO₂, Al₂O₃, and ZrO₂ coatings, respectively. X-ray diffraction studies showed that there are no crystalline peaks corresponding SiO₂, Al₂O₃, and ZrO₂ because the oxide coatings of the FeCo core are amorphous in nature. The scanning electron micrograph analysis depicted the cubic nature of the particles with mean particle size of about 45 nm. The maximum saturation magnetization of 205 emu/g …
Dyadic Green's Function Calculations On A Layered Dielectric/Ferrite Structure, H. How, X. Zuo, C. Vittoria
Dyadic Green's Function Calculations On A Layered Dielectric/Ferrite Structure, H. How, X. Zuo, C. Vittoria
Carmine Vittoria
Dyadic Green's function techniques have been applied to solve the transmission properties of a microstrip line fabricated on top of a single-crystal Y-type hexaferrite substrate. Current potentials are used to construct the Galerkin elements to facilitate solution accuracy even in the FMR region. Transmission coefficients of a microstrip line fabricated on a Y-type hexaferrite substrate were thus calculated, which compared reasonably well with measurements.
Magnetostriction Measurements On Thin-Films By A Slot-Line Ferromagnetic-Resonance Technique, S. A. Oliver, V. G. Harris, C. Vittoria
Magnetostriction Measurements On Thin-Films By A Slot-Line Ferromagnetic-Resonance Technique, S. A. Oliver, V. G. Harris, C. Vittoria
Carmine Vittoria
We report on a new technique for the determination of the linear magnetostriction constant of thin films. The technique uses the shift in ferromagnetic resonance (FMR) of a magnetostrcitive sample upon application of an external stress. A circular thin film is deposited onto a fused quartz place by ion beam sputter deposition. The place is mounted in a cantilever configuration, with the film suspended over the junction of a slot-line/coplanar guided structure. The slot line proved a rf magnetic field normal to the film place, tunable over the frequency range 0.1 GHz
Single Crystal Hexaferrite Phase Shifter At Ka Band, X. Zuo, P. Shi, S. A. Oliver, C. Vittoria
Single Crystal Hexaferrite Phase Shifter At Ka Band, X. Zuo, P. Shi, S. A. Oliver, C. Vittoria
Carmine Vittoria
A phase shifter was fabricated from a scandium doped M-type (SCM) barium hexaferrite single crystal substrate, and tested over microwave frequencies from 20 to 40 GHz and bias magnetic fields from 0 to 2 kOe. At a microwave frequency of 40 GHz and bias magnetic field of 1.3 kOe, the differential phase-shift rate was 42°/kOe mm and the loss rate was 0.7 dB/mm. The phase shifter utilized the large uniaxial Å field inherent in ScM single crystals, where the crystallographic c axis and the magnetic bias field were parallel to each other and in the substrate plane. The performance of …
Epitaxial Growth Of Pbfe₁₂O₁₉ Thin Films By Alternating Target Laser Ablation Deposition Of Fe₂O₃ And Pbo, A. L. Geiler, Y. He, S. D. Yoon, A. Yang, Y. Chen, V. G. Harris, C. Vittoria
Epitaxial Growth Of Pbfe₁₂O₁₉ Thin Films By Alternating Target Laser Ablation Deposition Of Fe₂O₃ And Pbo, A. L. Geiler, Y. He, S. D. Yoon, A. Yang, Y. Chen, V. G. Harris, C. Vittoria
Carmine Vittoria
Oriented M-type hexaferrite thin films are deposited using the alternating target laser ablation deposition (ATLAD) technique utilizing PbO and Fe₂O₃ targets. Crystallographic, dc magnetic, and microwave characterization results confirming the presence of a hexagonal PbFe₁₂O₁₉ phase are presented. We conclude that the ATLAD technique holds great promise for layer by layer deposition of various hexaferrite materials, the properties of which can be adjusted by varying the composition of the targets as well as the number of laser shots from each target during the deposition process. This would provide control over the uniaxial anisotropy fields and saturation magnetization values that was …
Quantum Nucleation And Thermal-Activation Of Vortex Rings In High-Tc Superconductors, H. Jiang, A. Widom, Y. Huang, T. Yuan, C. Vittoria, D. B. Chrisey, J. S. Horwitz
Quantum Nucleation And Thermal-Activation Of Vortex Rings In High-Tc Superconductors, H. Jiang, A. Widom, Y. Huang, T. Yuan, C. Vittoria, D. B. Chrisey, J. S. Horwitz
Carmine Vittoria
Vortex-ring nucleation by thermal activation and quantum-tunneling processes in high-Tc superconductors is discussed. The nonlinear resistance scales as eν-(J/J)ν. Thermal activation yields a critical index of v = 1, while quantum tunneling (without normal current dissipation) yields a critical index of v = 2. Current-voltage characteristics were measured on both disordered (low-Jc), ordered (c axis normal to the film plane, high-Jc) Y-Ba-Cu-O films, and microbridges below Tc. The data were examined in terms of both thermal-activation and quantum-nucleation models. For the disordered films, the v = 1 scaling law is in reasonable agreement with data, while v = 2 scaling …
Propagation Characteristic Of A Ferrite Image Guide, P. Kwan, C. Vittoria
Propagation Characteristic Of A Ferrite Image Guide, P. Kwan, C. Vittoria
Carmine Vittoria
The propagation of electromagnetic waves in a ferrite image line was theoretically formulated. The formulation was based upon the effective permeability approach. The ferrite image line consisted of an insulating slab of ferrite with a rectangular cross section overlaid on an electrical ground plane. The ferrite was purposely magnetically biased so that FMR coincided with the band of frequencies in which propagation is allowable in the waveguide structure. Insertion loss and phase shifts of the electromagnetic wave signal was calculated as a function of frequency. We suggest that ferrite phase shifters, isolators, filters, and switches operating at the millimeters wavelength …
Quantum-Electrodynamic Theory Of Vortex Oscillations In Type-Ii Superconductors, A. Widom, Y. N. Srivastava, C. Vittoria, H. How, R. Karim, H. Jiang
Quantum-Electrodynamic Theory Of Vortex Oscillations In Type-Ii Superconductors, A. Widom, Y. N. Srivastava, C. Vittoria, H. How, R. Karim, H. Jiang
Carmine Vittoria
In the quantum-electrodynamic theory of vortex motions in type-II superconductors, the energy stored in the electric field must be added to the conventional energy in the magnetic field. The resulting quantum-electrodynamic Hamiltonian produces the appropriate quantum vortex dynamics. The implications of the theory for vortex-induced irreversibility in type-II superconductors are also explored.
Intrinsic Ferromagnetic Resonance Linewidth Of Barium Ferrite Due To Spin-Wave Scattering By Trigonal Site Single-Particle Excitations, J. B. Sokoloff, S. P. Marshall, C. Vittoria
Intrinsic Ferromagnetic Resonance Linewidth Of Barium Ferrite Due To Spin-Wave Scattering By Trigonal Site Single-Particle Excitations, J. B. Sokoloff, S. P. Marshall, C. Vittoria
Carmine Vittoria
Time-dependent two-magnon scattering was previously proposed as a mechanism to explain the large magnitude of the ferrimagnetic resonance (FMR) linewidth of barium ferrite as a function of frequency. In the present work, it is shown that a quantum mechanical mechanism like the Kasuya-Le Craw process (KL) but with the phonon excitation replaced by a single-particle excitation of a trigonal site iron ion, which moves in an anharmonic potential well, gives a linewidth contribution of less than a tenth of an Oersted and proportional to the frequency, as in the KL mechanism. We conclude, based on this work and our previous …
Magnetic-Properties And Local Ordering During Thermal Annealing Of Amorphous Fe₇₅Ni5b₁₅Si₅ Films, S. A. Oliver, V. G. Harris, C. Vittoria, W. T. Elam, K. H. Kim, H. H. Hamdeh, M. Alhabash
Magnetic-Properties And Local Ordering During Thermal Annealing Of Amorphous Fe₇₅Ni5b₁₅Si₅ Films, S. A. Oliver, V. G. Harris, C. Vittoria, W. T. Elam, K. H. Kim, H. H. Hamdeh, M. Alhabash
Carmine Vittoria
The evolution of magnetic properties and local atomic ordering during thermal annealing has been studied for amorphous Fe₇₅Ni5B₁₅Si₅ thin films. Resistivity, vibrating sample magnetometer (VSM), ferromagnetic resonance (FMR), extended x-ray absorption fine structure (EXAFS), and Mossbauer effect (ME) measurements were taken on samples annealed at various temperatures ranging to film crystallization. The as-deposited samples are in a close-packed structure with little short-range order. Samples annealed above 200°C show ordering of the boron shell, but no indication of long-range ordering. With the exception of the anisotropy and coercive fields, no change in the magnetic or microwave magnetic parameters is observed for …
Electronic Tuning Of Magnetic Permeability In Co₂Z Hexaferrite Toward High Frequency Electromagnetic Device Miniaturization, Yajie Chen, Andrew Daigle, Trifon Fitchorov, Bolin Hu, Michael Geiler, Anton Geiler, C. Vittoria, V. G. Harris
Electronic Tuning Of Magnetic Permeability In Co₂Z Hexaferrite Toward High Frequency Electromagnetic Device Miniaturization, Yajie Chen, Andrew Daigle, Trifon Fitchorov, Bolin Hu, Michael Geiler, Anton Geiler, C. Vittoria, V. G. Harris
Carmine Vittoria
The magnetic and magnetostriction properties of Z-type cobalt-doped barium hexaferrite with perpendicular c-axis crystallographic texture are presented. The hexaferrite was utilized as a component in Co₂Z/lead magnesium niobate-lead titanate multiferroic heterostructures whose tunability of permeability with electric field in terms of ferromagnetic resonance shift was supported by experiments and theoretical calculation. A permeability change of 16% was measured by an induced magnetic field of 38 Oe under the application of 6 kV/cm of electric field. These findings lay the foundation for the application of Z-type hexaferrites in tunable rf and microwave devices valued for sending, receiving, and manipulating electromagnetic signals.
Microwave And Magnetic Properties Of Double-Sided Hexaferrite Films On (111) Magnesium Oxide Substrates, S. G. Wang, S. D. Yoon, C. Vittoria
Microwave And Magnetic Properties Of Double-Sided Hexaferrite Films On (111) Magnesium Oxide Substrates, S. G. Wang, S. D. Yoon, C. Vittoria
Carmine Vittoria
We have deposited hexaferrite films of BaFe₁₂O₁₉ on both sides of a magnesium oxide, (111) MgO, substrate by the liquid phase epitaxy (LPE) deposition technique. The procedure entailed the deposition of seed layers of BaFe₁₂O₁₉ onto the substrate by laser ablation deposition and then dipping of the substrate into a molten flux. Whereas the seed layers were the order of 0.5 μm, the total thickness after LPE deposition was ∽45 μm. The ferrimagnetic resonance linewidth at 60 GHz, 27 Oe, is as low as it has ever been measured before in BaFe₁₂O₁₉ to the best of our knowledge. The static …
Electron-Spin-Resonance In Single-Crystals Of Yba₂Cu₃O₇₋ₓ And Bi₄/₃Pb₂/₃Sr₂Cacu₂O₈₊ₓ, R. Karim, R. Seed, H. How, A. Widom, C. Vittoria, G. Balestrino, P. Paroli
Electron-Spin-Resonance In Single-Crystals Of Yba₂Cu₃O₇₋ₓ And Bi₄/₃Pb₂/₃Sr₂Cacu₂O₈₊ₓ, R. Karim, R. Seed, H. How, A. Widom, C. Vittoria, G. Balestrino, P. Paroli
Carmine Vittoria
We report on electron-spin resonance on single crystals of YBa₂Cu₃O₇₋ₓ and Bi₄/₃Pb₂/₃Sr₂CaCu₂O₈₊ₓ at 9 GHz, While in the YBCO there was no observable ESR signal in the normal state (above Tc) or in the superconducting state (below Tc), we did observe a large microwave nonresonant absorption below Tc at low field values (H < 200 Oe). We attribute this form of absorption to fluxoid formation below Tc. In the BiPbSrCaCuO single crystals, a significantly different result was found in that an electron-spin-resonance signal was measured both above and below Tc , besides the low-field absorption occurring only below Tc. The g …
Low-Field Dependence Of The Microwave-Absorption In Superconducting Yba₂Cu₃O₇₋ₓ Near Tc, R. Karim, S. A. Oliver, C. Vittoria, A. Widom, G. Balestrino, S. Barbanera, P. Paroli
Low-Field Dependence Of The Microwave-Absorption In Superconducting Yba₂Cu₃O₇₋ₓ Near Tc, R. Karim, S. A. Oliver, C. Vittoria, A. Widom, G. Balestrino, S. Barbanera, P. Paroli
Carmine Vittoria
Novel microwave absorption and dispersion measurements have been performed on polycrystalline samples and well-characterized single-crystal platelets of high-Tc superconductors YBa₂Cu₃O₇₋ₓ. The results are explained in terms of fluxoids and rapid variation of the penetration depth near and below Tc. The microwave absorption increases as a function of the magnetic field as a result of increase in the surface area of the normal-conducting region. By applying a modulating field in a particular manner and from thermodynamic considerations there are strong indications of energy absorption by fluxoids.