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Introduction The incidence of periprosthetic fractures after total knee arthroplasty (TKA) is increasing, and treatment is becoming more necessary. In periprosthetic tibial fractures, the stem of the tibial component largely occupies the medullary canal of the proximal tibia, which limits the selection of implants. The purpose of this study was to evaluate the effectiveness of the minimally invasive plate osteosynthesis (MIPO) technique with locking plates for periprosthetic tibial fractures after TKA. Materials and methods Sixteen patients with periprosthetic tibial fracture after TKA were included. There were 6 type II and 10 type III fractures according to the Felix classification. Ten patients had fractures in the proximal metaphysis, and 6 in the diaphysis. MIPO using locking plates was performed on the medial side in 4 cases, the lateral side in 2 cases, and both in 10 cases. Radiographic results included time to union, alignment, and malunion. Clinical results included range of motion (ROM), functional activity data, Knee Society scores, and complications. Results Fourteen of 16 fractures achieved union at 17.1 weeks (range, 14–24) postoperatively. There were 2 failures that required a secondary procedure. Except one for 1 case with varus malunion, all had acceptable alignment. Mean ROM at the final follow-up was 108.8° (range, 15–135°), and 15 patients recovered pre-injury knee joint activity. Mean knee and function scores were 88.9 (range, 77–100) and 83.3 (range, 60–100), respectively. Knees with fewer than 8 cortices giving purchase to screws in the proximal segment showed higher failure rates (P = 0.025). Discussion MIPO with locking plates can achieve satisfactory results for periprosthetic tibial fractures after TKA. Rigid fixation of the proximal segment may be necessary for successful outcome. Level of evidence IV.

A microstrip line fabricated on a single crystal hexagonal Y-type ferrite substrate was utilized to achieve phase shifts of ~65deg/cm at KU-band with an external bias field of only 100 Oe. This approach utilizes the rapid variation of the Y-type ferrite tensor permeability near the ferromagnetic antiresonance frequency. The magnetic and microwave properties of the substrate material were characterized by vibrating sample magnetometry and ferromagnetic resonance measurements. Numerical methods based on Galerkin's approach adapted to spectral domain were utilized to model the performance of the device while taking into account the correct form of the tensor magnetic permeability of the anisotropic and gyromagnetic substrate material. Good agreement between the numerical results and experimental data was obtained. A miniature electromagnet, based on a Metglastrade laminated yoke to minimize demagnetizing fields, was fabricated. Phase shifts of 50deg/cm were achieved with continuous drive currents of only 100 mA.

Next generation magnetic microwave devices will be planar, smaller, weigh less, and perform well beyond the present state-of-the-art. For this to become a reality advances in ferrite materials must first be realized. These advances include self-bias magnetization, tunability of the magnetic anisotropy, low microwave loss, and volumetric and weight reduction. To achieve these goals one must turn to novel materials processing methods. Here, we review recent advances in the processing of microwave ferrites. Attention is paid to the processing of ferrite films by pulsed laser deposition, liquid phase epitaxy, spin spray ferrite plating, screen printing, and compaction of quasi-single crystals. Conventional and novel applications of ferrite materials, including microwave non-reciprocal passive devices, microwave signal processing, negative index metamaterial-based electronics, and electromagnetic interference suppression are discussed.

The deposition and characterization of high quality ferrite thin films by the alternating target laser ablation deposition (ATLAD) technique is discussed with the emphasis on the unique magnetic properties induced in these materials by stabilizing far from equilibrium cation distributions. Two spinel systems and three hexagonal ferrite systems are studied. In the case of manganese spinel ferrite a large in-plane uniaxial anisotropy field ( > 5 kOe) is induced in ATLAD deposited films. In the case of copper spinel ferrite a 65% enhancement in the saturation magnetization is observed over the bulk value. In the case of manganese substituted barium ferrite a 12-22% enhancement in low temperature saturation magnetization and 40-60 K increase in the Neel temperature is observed. The unique magnetic properties of the films are correlated with the cation distributions stabilized by the application of the ATLAD technique as determined by the extended X-ray absorption fine structure (EXAFS) analysis.

Epitaxial manganese substituted M-type barium ferrite thin films are deposited by alternating target laser ablation deposition (ATLAD) of BaFe2O4, Fe2O3, and MnFe2O4 targets. The crystal structure and the epitaxy of the films are investigated by X-ray diffraction. Surface morphology is studied by atomic force microscopy. Magnetic properties of the films are characterized by vibrating sample magnetometry and magnetization as a function of temperature measurements. Ferromagnetic resonance (FMR) measurements are utilized to study the dynamic properties of the films. Possible mechanisms for main FMR linewidth broadening as a result of Mn substitution, such as increased conductivity and the presence of Jahn-Teller effect associated with octahedrally coordinated Mn3+ cations, are briefly discussed. Extended absorption X-ray fine structure measurements are performed to determine the cation distribution in the hexagonal unit cell. The observed 15-20% increase in saturation magnetization at 4 K and 50 K increase in the Neel temperature in comparison to bulk reference values are attributed to differences in cation distribution as a result of atomic scale deposition by the ATLAD technique.

A magnetic field tunable, broadband, low-loss, negative refractive index metamaterial is fabricated using yttrium iron garnet (YIG) and a periodic array of copper wires. The tunability is demonstrated from 18 to 23 GHz under an applied magnetic field with a figure of merit of 4.2 GHz/kOe. The tuning bandwidth is measured to be 5 GHz compared to 0.9 GHz for fixed field. We measure a minimum insertion loss of 4 dB (or 5.7 dB/cm) at 22.3 GHz. The measured negative refractive index bandwidth is 0.9 GHz compared to 0.5 GHz calculated by the transfer function matrix theory and 1 GHz calculated by finite element simulation.

We demonstrate a semiconducting material, TiO{sub 2-{delta}}, with magnetism up to 880 K, without the introduction of magnetic ions. The magnetism in these films stems from the controlled introduction of anion defects from both the film substrate interface as well as processing under a deficient oxygen atmosphere. First-principle band structure calculations indicate that the exchange between Ti cations mediated by an oxygen anion is positive, i.e., ferromagnetic, whereas the exchange between cations via a vacancy is negative, i.e., ferrimagnetic. It is likely that both the mechanisms are active in this system. This represents a new and promising approach in the search for room-temperature magnetic semiconductors.

We demonstrate a semiconducting material, TiO2??, with ferromagnetism up to 880?K, without the introduction of magnetic ions. The magnetism in these films stems from the controlled introduction of anion defects from both the film?substrate interface as well as processing under an oxygen-deficient atmosphere. The room-temperature carriers are n-type with n~3 ? 1017?cm?3. The density of spins is ~1021?cm?3. Magnetism scales with conductivity, suggesting that a double exchange interaction is active. This represents a new approach in the design and refinement of magnetic semiconductor materials for spintronics device applications.

Barium hexaferrite films have been processed by pulsed laser deposition on single crystal 6-H silicon carbide substrates. Atomic force microscopy images show hexagonal crystals (∼0.5 μm in diameter) oriented with the c-axis perpendicular to the film plane. X-ray θ–2θ diffraction measurements indicate a strong ( 0 , 0 , 2 n ) alignment of crystallites. The magnetization for low-pressure deposition (20 mTorr) is comparable to bulk values (4πMs∼4320 G). The loop squareness, important for self-bias microwave device applications, increases with oxygen pressure reaching a maximum value of 70%. This marks the first growth of a microwave ferrite on SiC substrates and offers a new approach in the design and development of μ-wave and mm-wave monolithic integrated circuits.

The deposition and characterization of thick M-type barium hexaferrite (BaFe12O19) films produced by a modified liquid phase epitaxy deposition technique are reported. The films are deposited on (111) oriented single crystal garnet (Gd3Ga5O12) substrates. The thickness of the films ranged between 45 and 80μm with growth rates of up to 40μm∕h. This growth rate is about five times greater than films grown on substrates of (111) magnesium oxide. Although the films are relatively thick, the ferrimagnetic resonance linewidth is remarkably narrow (∼50Oe) for external fields applied along the c axis.

Highly oriented films of ( 1 0 1 0 ) BaSc0.6Fe11.4O19 having the magnetic easy axis (crystallographic [0 0 0 1] axis) in the film plane were deposited by pulsed laser deposition onto a-plane ( 1 1 2 0 ) sapphire (Al2O3) substrates. Magnetometry and torque magnetometry measurements showed in-plane permanent magnet (magnetic dipole) behavior below a coercive field value of 450 Oe, while high field measurements yielded a uniaxial anisotropy field value of 10 kOe. Measurements at temperatures from 123 to 650 K showed the uniaxial anisotropy field was insensitive to temperature for T

Thick (1–14 μm) films of ferrimagnetic barium hexaferrite (BaFe12O19 or BaM) having the c-axis ([0001]) in the film plane were deposited by pulsed laser deposition onto a-plane (112¯0) sapphire (Al2O3) substrates, and were found to have a (101¯0) orientation. Torque and magnetization measurements show these films are permanent magnets with easy magnetization direction in the plane of the film. Ferrimagnetic resonance (FMR) spectra exhibited linewidths of 1.00–1.40 kOe, where low-field FMR measurements do not show uniform mode broadening due to the formation of multiple domains. All film parameters were affected by the large stress present in these films due to crystallographic and thermal mismatches. These films have dual functionality as gyrotropic media and permanent magnets, and are usable as either nonreciprocal microwave devices or biasing magnets.

This work examines the material characteristics and magnetic properties of hexagonal M-type barium ferrite (BaFe12O19) films deposited by pulsed laser ablation deposition onto (111) magnesium oxide substrates at different oxygen growth pressures. X-ray diffraction data showed the lattice constant of the film grown at 300 mTorr c=23.23 A increased to c=23.30 A for the film grown at 20 mTorr. The saturation magnetization ranged from 4.03 to 4.33 kG and the magnetic uniaxial anisotropy field ranged from 16.73 to 19.49 kOe as the oxygen pressure was varied from 10 to 300 mTorr. The narrowest ferrimagnetic resonance (FMR) linewidths (ΔH) for as-produced films were obtained for the 10 mTorr films, where ΔH=0.39 kOe. Films grown with oxygen pressure at 200 mTorr or higher showed two distinct resonance modes, which exhibited ΔH1⩾0.90 kOe and ΔH2⩾1.10 kOe at 59 GHz for a film deposited at 925 °C. The FMR linewidths for this film decreased to ΔH1=0.52 kOe and ΔH2=0.45 kOe after annealing the film at 1000 °C for 1 h...

We report the fabrication of planar microstripline reciprocal phase shifter using a bulk Yttrium Iron Garnet (YIG) material. The propagation direction of the microstripline and magnetization direction of the YIG is collinear, and the length of the microstripline and the YIG was 50 mm in length. The proposed design shows large differential phase shifts of 100 degrees for applied magnetic fields varying from 0 to 0.56 times 104 A/m over the frequency range of 1.2 GHz between 5.4 GHz and 6.6 GHz. The average insertion loss, ~ 2.5 dB, was measured to have a 20% bandwidth at 6 GHz. The planar phase shifter presented here demonstrates a compact design, low loss, and an especially large phase shift with a relatively small bias field.

Magnetoelectric behavior of a yttrium iron garnet (YIG)/zirconate titanate (PZT) magnetoelectric bilayer composite was studied over 1-7 GHz under different bias magnetic fields and electric fields by using a broadband air-gap microstrip with the PZT/YIG loaded in the air gap. Electrostatically induced ferrimagnetic resonance (FMR) frequency shifts of the YIG/PZT bilayer composite were studied. The FMR frequency shift was negligible at bias fields when the YIG was not saturated. After saturation, the FMR frequency increased nearly linearly from 15 MHz at a bias field of 100 Oe to 30 MHz at 1200 Oe and dropped suddenly at a field of 1300 Oe to about 20 MHz. This nonlinear bias magnetic held dependence was due to magnetic domain activities when the YIG was not saturated and due to the interference between the uniform mode and other magnetostatic spin waves after saturation. An electrostatically tunable band-reject filter device was demonstrated which has a peak attenuation of greater than 50 dB, 40 dB rejection band of 10 MHz, and pass band insertion loss of

We have designed and simulated a circulator circuit in which the magnetization aligns along the plane of an yttrium iron garnet (YIG) film. For an X-band frequency (8-12 GHz) circulator we have utilized a YIG slab (~200 mum thick) with saturation magnetization (4piMS ) and ferrimagnetic resonance (FMR) linewidth (DeltaH) of ~139.26 kA/m and 10 Oe, respectively. Broadband circulator operation was realized for frequencies above FMR, f=5 GHz. The applied FMR field was 79.58 kA/m. The Ansoft HFSS software suite was used to simulate the circulator response. The insertion loss S21 and the isolation S12 were calculated to be ~0.9 dB and ~-52 dB, respectively, with ~15% bandwidth at the center frequency of 10.1 GHz. We believe that this in-plane circulator design may enable high performance with significant volume and weight reduction

Ferromagnetic (FM)/antiferromagnetic (AFM)/ferromagnetic trilayers of Ru seeded Co90Fe10/Pt50Mn50 /Co90Fe10 and Co84Fe16/Pt50Mn50/Co84 Fe16 were deposited, and their magnetic properties characterized at dc and at microwave frequencies. A ferromagnetic resonance (FMR) linewidth of 45 Oe at X-band (~9.5 GHz) was achieved in the Co84Fe16/Pt50Mn50/Co84 Fe16 trilayer. The minimum FMR linewidth occurs at an intermediate CoFe thickness, which is in contrast to the typical monotonic drop of FMR linewidth with the increment of FM layer thickness in the exchange-coupled FM/AFM bilayers. The CoFe/PtMn/CoFe trilayers show significantly enhanced anisotropy field up to 340 Oe at X band, which is more than double of that at dc frequency, indicating an obvious discrepancy between the anisotropy field at dc and at X band

M-type barium hexaferrite films were processed by pulsed laser deposition on single-crystal 6-H silicon carbide substrates. MgO buffer and barrier layers were introduced to improve the film quality. Samples were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, X-ray diffraction, vibrating sample magnetometry, and ferromagnetic resonance (FMR). X-ray thetas-2thetas diffraction measurements indicated a strong (0, 0, 2n) crystallographic alignment. The magnetization of the BaM film is comparable to bulk values (4piMs~4320 G). A derivative power FMR linewidth of 500 Oe was measured at 55 GHz for the as-deposited films. This paper explores a potential next generation of microwave and millimeter-wave monolithic integrated circuit technology based upon a wide band-gap semiconducting material

In this paper, we report on the deposition of thick and high-quality films of BaM on (111) gadolinium gallium garnet (GGG) and m-plane, (11_00) or (101_0), sapphire (Al/sub 2/O/sub 3/) substrates. The deposition rate is sufficiently high to allow for large batch production. The total thickness ranged from 50 to 200 /spl mu/m for 2 h of the liquid phase epitaxy deposition. Therefore, the growth rate of the films ranged from /spl sim/25 to /spl sim/100 /spl mu/m/h. In previous work, growth rates in BaM films were quite small. Equally important, the ferrimagnetic resonance (FMR) linewidth (/spl Delta/H) was /spl sim/0.068 kOe at 58 GHz for the BaM films on (111) GGG and /spl sim/0.08 kOe at 59.9 GHz for the BaM film on m-plane sapphire substrates. The FMR linewidth films of thick BaM films deposited by pulsed laser deposition in earlier work ranged from 0.5 to 1.2 kOe.

We report the growth of thick barium hexaferrite (BaFe12O19,BaM) films on m-planes ([11_00] or [101_0]) sapphire (Al2O3) substrates by the liquid phase epitaxy deposition technique. The procedure entailed the deposition of seed layers of BaFe12O19 onto the substrate by the pulsed laser ablation deposition and then dipping the substrate into a molten flux for 2 h. The total thickness ranged from 60 μm to 200 μm. The vibrating sample magnetometer (VSM) measurement data showed that the film exhibited magnetic uniaxial anisotropy axis in the film plane. The coercive field was relatively small, range of Hc was from 0.007 kOe to 0.08 kOe, and the saturation magnetization (4πMs)≅4.42 kG. The ferrimagnetic resonance (FMR) linewidth (ΔH) at 59.9 GHz was ∼0.08 kOe. This value of ΔH should be contrasted with previous FMR linewidth measurement of films deposited by the PLD technique which showed a ΔH of ∼1.20 kOe.

M-type barium hexaferrite films have been grown by liquid phase epitaxy and examined by x-ray diffraction,scanning electron microscopy, atomic force microscopy, and conventional and Lorentz-mode transmission electron microscopy(TEM). These films exhibit a diamond chevron shaped “brick wall” microstructure with c-axis oriented hexaferrite platelets. The films are oriented with their c axes in-plane, and parallel to the M-plane sapphire substrate, and exhibit a 30° rotation about the c axis with respect to the substrate. Rocking curves showed (20−20) and (22−40) FWHM values of 1.09° and 1.56°, respectively, for the thinner of two samples, and 0.31° and 0.50° for the thicker sample. The magnetic domain structures have been characterized by Lorentz-mode TEM and the domain walls were found to be pinned to small angle tilt boundaries. Using the measured rocking curve values, the effect of the overall crystalline misorientation on the dispersion of the magnetocrystalline anisotropy of the samples is estimated to be less than half a percent.

C-axis oriented barium hexaferrite films having thickness from 3-30 /spl mu/m were deposited onto 0.5 mm magnesium oxide (MgO) [111] substrates by pulsed laser ablation deposition, and were characterized by magnetometry and ferrimagnetic resonance (FMR) measurements. The FMR linewidth for as-produced 30 /spl mu/m films was 0.65-0.70 kOe, while those of thinner (3 /spl mu/m) films was near 0.50 kOe. The narrowest linewidth of /spl sim/0.06 kOe was obtained for a 3 /spl mu/m film after annealing for two hours. However, increased annealing time beyond two hours caused an increase in FMR linewidth. The FMR linewidth of 30 /spl mu/m films where from 55-77% of the MgO substrate was removed decreased by 0.15-0.20 kOe compared to as-produced films. Further improvement in the FMR linewidth to 0.20 kOe was obtained by a two hour annealing. These FMR results are discussed in terms of the homogeneity, planar stress, and stoichiometry of these thick pulsed laser deposited films.

The phenomenological equations of motion for the relaxation of ordered phases of magnetized and polarized crystal phases can be developed in close analogy with one another. For the case of magnetized systems, the driving magnetic field intensity toward relaxation was developed by Gilbert. For the case of polarized systems, the driving electric field intensity toward relaxation was developed by Khalatnikov. The transport times for relaxation into thermal equilibrium can be attributed to viscous sound wave damping via magnetostriction for the magnetic case and electrostriction for the polarization case., Comment: 5 pages no figures ReVTeX 4

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.

The properties of thick BaScxFe12−xO19 (0.3

A Comment on the Letter by M. C. Hickey and J. S. Moodera, Phys. Rev. Lett. 102, 137601 (2009). The authors of the Letter offer a Reply.

Cobalt carbide nanoparticles were processed using polyol reduction chemistry that offers high product yields in a cost effective single-step process. Particles are shown to be acicular in morphology and typically assembled as clusters with room temperature coercivities greater than 4 kOe and maximum energy products greater than 20 KJ/m3. Consisting of Co3C and Co2C phases, the ratio of phase volume, particle size, and particle morphology all play important roles in determining permanent magnet properties. Further, the acicular particle shape provides an enhancement to the coercivity via dipolar anisotropy energy as well as offering potential for particle alignment in nanocomposite cores. While Curie temperatures are near 510K at temperatures approaching 700 K the carbide powders experience an irreversible dissociation to metallic cobalt and carbon thus limiting operational temperatures to near room temperature., Total 28 pages, 10 figures, and 1 table

Ferrite phase shifter devices having drastically reduced bias field requirements are demonstrated at C and Ku band utilizing polycrystalline YIG and single crystal hexagonal Y-type ferrite materials. Phase shifts on the order of 100 degrees with bias fields below 100 Oe are achieved. A novel numerical analysis method for modeling anisotropic ferrites is presented and a good agreement between calculation results and experimental data achieved. Methods of generating tuning magnetic fields with small current drives are presented. The possibility of realizing voltage tuning of ferrite devices via the magnetoelectric effect and preliminary experimental results are discussed. Numerical modeling of meander line phase shifter designs with figures of merit in excess of 200 degrees per dB of insertion loss are presented.

Mn ferrite (MnFe(2)O(4)) nanoparticles, having diameters from 4 to 50 nm, were synthesized using a modified co-precipitation technique in which mixed metal chloride solutions were added to different concentrations of boiling NaOH solutions to control particle growth rate. Thermomagnetization measurements indicated an increase in Neel temperature corresponding to increased particle growth rate and particle size. The Neel temperature is also found to increase inversely proportionally to the cation inversion parameter, delta, appearing in the formula (Mn(1-delta)Fe(delta))(tet)[Mn(delta)Fe(2-delta)](oct)O(4). These results contradict previously published reports of trends between Neel temperature and particle size, and demonstrate the dominance of cation inversion in determining the strength of superexchange interactions and subsequently Neel temperature in ferrite systems. The particle surface chemistry, structure, and magnetic spin configuration play secondary roles.

We have formulated a relaxation mechanism for ferrites and ferromagnets (insulators and metals) whereby the coupling between the magnetic motion and lattice is based purely on continuum arguments concerning magnetostriction. This theoretical approach contrasts with previous mechanisms based on microscopic formulations of spin-phonon interactions employing a discrete lattice. Our model explains the scaling of the intrinsic ferromagnetic resonance linewidth with frequency, with temperature ${\ensuremath{\propto}1/{M}_{s}(T)}$ and the anisotropic nature of magnetic relaxation in ordered magnetic materials. Here, ${M}_{s}(T)$ is the thermal saturation magnetization. Without introducing adjustable parameters, our model is in reasonable quantitative agreement with experimental measurements of the intrinsic magnetic resonance linewidths of important class of ordered magnetic materials including both insulators and metals.

Using a novel alternating target laser ablation deposition technique, Mn cations were placed in specific interstitial sites of BaFe12O19 thin films as opposed to being distributed throughout the unit cell as in conventional bulk materials. The distribution of Mn cations has been confirmed experimentally and predicted theoretically. As a result of site selection, the saturation magnetization increased 12%-22%, and the Neel temperature increased by 40-60 K compared to bulk materials. This technique implies a new methodology to design and process a new generation of ferrite, oxide, and alloy materials.

TiO$_{2-\delta}$ films were deposited on (100) Lanthanum aluminates LaAlO$_{3}$ substrates at a very low oxygen chamber pressure $P\approx 0.3$ mtorr employing a pulsed laser ablation deposition technique. In previous work, it was established that the oxygen deficiency in these films induced ferromagnetism. In this work it is demonstrated that this same oxygen deficiency also gives rise to semiconductor titanium ion impurity donor energy levels. Transport resistivity measurements in thin films of TiO$_{2-\delta}$ are presented as a function of temperature and magnetic field. Magneto- and Hall- resistivity is explained in terms of electronic excitations from the titanium ion donor levels into the conduction band., Comment: RevTeX4, Four pages, Four Figures in ^.eps format

In this paper, the authors examined the ferromagnetic resonance (FMR) characteristics of CoFe/PtMn/CoFe trilayer thin films to determine mechanisms behind the intermediate drop in linewidth observed, and investigate the exchange bias fields (Hex) at DC versus at X-band (9.5 GHz). Results showed that the FMR linewidth did not drop monotonically with the increase of FM thickness in the exchange coupled trilayers. This non-monotonic FMR linewidth drop could be utilized in integrated microwave magnetic materials for RF and microwave devices.

High quality films of barium hexaferrite (BaFe12O19) were deposited by pulsed laser ablation onto MgO (111) substrates. In contrast to previous films deposited onto c-plane sapphire (Al203), these films were expected to have compressive biaxial stress, and indeed showed no indications for either cracking or delamination to a film thickness of 32 νm. All films were found to be highly c-axis textured by both x-ray diffraction measurements and magnetization results. The saturation magnetization (4πMs = 4.2 kG) and uniaxial anisotropy field (HA = 16 kOe) values for these films approach bulk values. Ferrimagnetic resonance measurements on a calcined 3 μm thick film show a narrow linewidth (ΔH ∼ 100 Oe) for the uniform resonance mode. The properties of these films approach those required for self-biased millimeter wavelength devices.

Experimental results are shown for the structural and stress behaviors of c-axis oriented barium hexaferrite films on c-plane sapphire (Al2O3) substrates as a function of oxygen growth pressure and film thickness. It is shown that films deposited at 20 mTorr crack and delaminate at thicknesses above 15 µm, but that evidence for these large stresses is not apparent in either substrate curvature measurements or distortion of the c-axis lattice constant for thinner films (< 2 µm). In contrast, films (< 4 µm) deposited at 300 mTorr show large substrate curvatures that relax with increasing film thickness, in tandem with the formation of first large outgrowths, and then polycrystalline grains as the original c-axis film texture is randomized. Correlations between these observations are made to explain the complex evolution of properties in these films.

Barium hexaferrite films having thickness from 3 to 30 μm were deposited onto 0.5 mm Magnesium Oxide (111) substrates, and were examined by vibrating sample magnetometry, torque magnetometry, x-ray diffraction, and scanning electron microscope measurements. Ferrimagnetic resonance measurements were taken with the magnetic field applied perpendicular to the film plane. The FMR linewidth values for as-produced 3 - 30 μm films was 0.45 - 0.70 kOe, and was reduced to 0.06 - 0.45 kOe after annealing at 1000 °C for 2 hours. Further annealing increased the linewidth. The FMR linewidth for the 30 μm thick film was also found to decrease upon mechanically removing 55 ∼ 77 % of the substrate thickness. A 6-fold in-plane anistropy symmetry in the anisotropy energy was observed in torque magnetometry measurements for films thicker than 30 μm. These results can be interpreted as due to film inhomogeneity, stress, and the growth of small regions of non c-axis textured material.

Thick films of scandium-substituted BaScxFe12−xO19 (x=0, 0.4, 0.6) were deposited by pulsed laser ablation deposition onto A-plane (1120) sapphire (Al2O3) substrates to yield highly oriented films having the crystallographic c-axis ([0001]) in the film plane. Selected films were characterized by x-ray diffraction, electron microscopy, magnetometry and torque magnetometry measurements. These structural and magnetic measurements show that dense films have excellent in-plane uniaxial anisotropies and good square loop behaviors. Such films will be useful for planar latched phase shifters that can be integrated into microwave integrated circuits.

Liquid-phase epitaxy deposition has been investigated to obtain thick and high quality of barium hexaferrite films on (1 1 1) gadolinium gallium garnet (GGG) and m-plane (1 1 0 0) aluminum oxide (Al 2 O 3 ) substrates. For films deposited on (1 1 1) GGG substrate the c -axis was aligned perpendicular to the film plane, but in the plane for films deposited on Al 2 O 3 . The films were deposited on both sides of the substrates, where the total thickness of the films ranged between 70 and 190 μm. The thickness and quality of these films meet the requirement for applications at high frequencies.

The phenomenological Gilbert–Landau–Lifshitz theory of magnetic damping in ordered magnetic materials has long served as the central model employed in the analysis of considerable experimental magnetic resonance data. The problem undertaken here is to formulate the microscopic basis of the model in terms of usual theory of irreversible transport embodied in the fluctuation-dissipation-response theorems. As an application of the general method we establish a rigorous relationship between magnetic damping and acoustic damping implicit in magnetoelastic models.

FexCo100−x nanoparticles were synthesized by aqueous reduction in iron (II) sulfate and cobalt (II) sulfate using sodium borohydride and sodium citrate. The initial concentrations of iron and cobalt were varied while maintaining an overall metal concentration of 4.60 mM. Increasing the cobalt content from 0 to 100 at. % decreased the magnetization saturation from 152 to 48 emu/g, as determined by room temperature vibrating sample magnetometry. Annealing the samples at 450 and 600 °C showed an increase in crystallite size. Powder x-ray diffraction and transmission electron microscopy was performed to determine the phases and morphology of the materials.

Magnetic fringe fields emanating from a multiferroic heterostructure composite of Terfenol-D and lead magnesium niobate-lead titanate were utilized to actively tune a meander line microstrip ferrite phase shifter operating above ferrimagnetic resonance at C-band. Differential phase shifts of 65° were measured when tuned with an applied voltage to the multiferroic heterostructure. This demonstration of magnetoelectric field generation provides an alternative approach to tuning broadband planar microwave magnetic devices where neither strain nor direct electromagnetic coupling is experienced between device and multiferroic transducer.

A strong magnetoelectric (ME) interaction is presented in a magnetostrictive-semiconductor-piezoelectric heterostructure that consists of the Huesler alloy, Co2MnAl, GaAs, and lead magnesium niobate-lead titanate (PMN-PT). The laminated Co2MnAl/GaAs/PMN-PT structure, having a thickness of 19 nm/180 μm/500 μm, demonstrates a ferromagnetic resonance (FMR) field shift of 28 Oe with an external electric field of 200 V across the PMN-PT substrate. This corresponds to a resonance frequency shift of ∼125 MHz at X-band. It yields a large ME coupling (7 Oe cm/kV) and microwave tunability (∼32 MHz/kV cm−1), compared to other trilayer multiferroic composite structures. In addition, static magnetization measurement indicates a reduction in the remanence magnetization while applying the electric field, which corroborates the ME interactions mediated by the translation of magnetoelastic forces in this structure. This work explores the potential of multiferroic heterostrucuture transducers for use in FMR microwave devic...

The ferromagnetism induced by the intrinsic point defects in wurtzite zinc oxide is studied by using ab initio calculation based on density functional theory. The calculations show that both oxygen interstitial and zinc vacancy may induce ferromagnetism into this material. The calculations also show that zinc oxide with oxygen interstitial may be a ferromagnetic semiconductor. Based on the simplified electronic configuration of the defect molecules, we explain the total magnetic moment, electronic structure, and ferromagnetism.

The tuning of Neel temperature by greater than 100 K in nanoparticle Mn-ferrite was demonstrated by a growth-rate-induced cation inversion. Mn-ferrite nanoparticles, having diameters from 4 to 50 nm, were synthesized via coprecipitation synthesis. The Neel temperature (TN) increased inversely to the cation inversion parameter, δ (i.e., defined as (Mn1−δFeδ)tet[MnδFe2−δ]octO4). Concomitantly, TN increased with increased particle growth rate and particle size. These results unambiguously establish cation inversion as the dominant mechanism in modifying the superexchange leading to enhanced TN. The ability to tailor TN enables greater flexibility in applying nanoparticle ferrites in emerging technologies.

Nano granular metallic iron (Fe) and titanium dioxide (TiO$_{2-\delta}$) were co-deposited on (100) lanthanum aluminate (LaAlO$_3$) substrates in a low oxygen chamber pressure using a pulsed laser ablation deposition (PLD) technique. The co-deposition of Fe and TiO$_2$ resulted in $\approx$ 10 nm metallic Fe spherical grains suspended within a TiO$_{2-\delta}$ matrix. The films show ferromagnetic behavior with a saturation magnetization of 3100 Gauss at room temperature. Our estimate of the saturation magnetization based on the size and distribution of the Fe spheres agreed well with the measured value. The film composite structure was characterized as p-type magnetic semiconductor at 300 K with a carrier density of the order of $ 10^{22} /{\rm cm^3}$. The hole carriers were excited at the interface between the nano granular Fe and TiO$_{2-\delta}$ matrix similar to holes excited in the metal/n-type semiconductor interface commonly observed in Metal-Oxide-Semiconductor (MOS) devices. From the large anomalous Hall effect directly observed in these films it follows that the holes at the interface were strongly spin polarized. Structure and magneto transport properties suggested that these PLD films have potential nano spintronics applications., Comment: 6 pages in Latex including 8 figures

Scandium (Sc) doped, single phase BaFe12−xScxO19 (x=0.3 and 0.8) were prepared at large scale (10g) by a modified chemical coprecipitation technique. The scanning electron micrograph analysis shows the formation of nearly uniform hexagonal platelets with an average size of