A. Daigle

Planar Annular Ring Antennas With Multilayer Self-Biased NiCo-Ferrite Films Loading

With their high relative permeability, magneto-dielectric materials show great potential in antenna miniaturization. This paper presents an annular ring antenna with self-biased magnetic films loading in the gigahertz frequency range. The annular ring antenna was realized by cascading a microstrip ring and a tuning stub. Self-biased NiCo-ferrite films were adopted to load an annular ring antenna on a commercially available substrate that operates at 1.7 GHz. Novel antenna designs with self-biased NiCo-ferrite films on one side and both sides of the substrate were investigated. Antennas with self-biased magnetic films loading working at 1.7 GHz showed a down shift of 2-71 MHz of the central resonant frequency. An antenna gain enhancement of up to 0.8 dB was observed over the non-magnetic antenna.

Tunable Miniaturized Patch Antennas With Self-Biased Multilayer Magnetic Films

Magneto-dielectric substrates with thin magnetic films show great potential in realizing electrically small tunable antennas with enhanced bandwidth, improved directivity, and high efficiency. This communication introduces self-biased NiCo-ferrite magnetic films as a practical mean to tune a patch antenna by loading single layer and multilayer self-biased ferrite films. The central resonant frequency of the unloaded patch antenna is measured at 2.1 GHz with a bandwidth of 18 MHz. However, with ferrite loading of the alumina substrate, this frequency is shown to be tunable within a range of 12 MHz-40 MHz, and the antenna efficiency is increased from 41% of the non-magnetic antenna to 56%, 65%, and 74% for the three magnetic antennas. Theomnidirectional radiation pattern is significantly enhanced with the -5 dBic gain beamwidth increased from 140deg to 155deg, 156deg and 160deg, respectively for the three ferrite loaded antennas. In addition, the gains of the three magnetic antennas are enhanced by 0.32, 0.77, and 1.1 dB, respectively, over the unloaded antenna.

Electronically Tunable Miniaturized Antennas on Magnetoelectric Substrates With Enhanced Performance

Achieving relative permeability larger than 1 in antenna substrates can lead to antenna miniaturization, enhanced bandwidth, and tunable resonant frequency. Metallic magnetic films and self-biased ferrite films were introduced as a practical means to tune a patch antenna by loading a commercially available substrate in this paper. Novel antenna designs with metallic magnetic films and self-biased NiCo-ferrite films were investigated. Magnetic patch antennas were demonstrated at 2.1 GHz with a tuning resonant frequency range of 5-10 MHz (with the metallic magnetic films) and 7-23 MHz (with self-biased ferrite films). Three different cases of annular ring antennas with NiCo-ferrite films loading were also designed and analyzed. Antennas with self-biased magnetic films loading working at 1.7 GHz with a tuning range of 3-20 MHz were achieved.

Electronic tuning of magnetic permeability in Co2Z hexaferrite toward high frequency electromagnetic device miniaturization

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.

Structure, morphology and magnetic properties of Mg(x) Zn(1 − x)Fe2O4 ferrites prepared by polyol and aqueous co-precipitation methods: a low-toxicity alternative to Ni(x)Zn(1 − x)Fe2O4 ferrites

The synthesis and properties of Mg((x))Zn((1 - x))Fe(2)O(4) spinel ferrites as a low-toxicity alternative to the technologically significant Ni((x))Zn((1 - x))Fe(2)O(4) ferrites are reported. Ferrite nanoparticles have been formed through both the polyol and aqueous co-precipitation methods that can be readily adapted to industrial scale synthesis to satisfy the demand of a variety of commercial applications. The structure, morphology and magnetic properties of Mg((x))Zn((1 - x))Fe(2)O(4) were studied as a function of composition and particle size. Scanning electron microscopy images show particles synthesised by the aqueous co-precipitation method possess a broad size distribution (i.e. ∼ 80-120 nm) with an average diameter of the order of 100 nm ± 20 nm and could be produced in high process yields of up to 25 g l(-1). In contrast, particles synthesised by the polyol-based co-precipitation method possess a narrower size distribution with an average diameter in the 30 nm ± 5 nm range but are limited to smaller yields of ∼ 6 g l(-1). Furthermore, the polyol synthesis method was shown to control average particle size by varying the length of the glycol surfactant chain. Particles prepared by both methods are compared with respect to their phase purity, crystal structure, morphology, magnetic properties and microwave properties.

Numeric Simulations of a Novel Wideband Electromagnetic Band Gap Metamaterial Utilizing Oriented Cobalt-Substituted Z-Type Barium Hexaferrites

The material parameters of an electromagnetic bandgap (EBG) metamaterial consisting of metallic Sievenpiper structures prepared upon a Co2Z hexaferrite substrate having μr = 12 to 14 and εr = 10 to 12 are reported. A bandwidth of 50%-75% of L-band was realized in simulation. The synthesis of the Co2Z hexaferrite material with optimized properties was achieved via a modified aqueous coprecipitation method with yields of up to 25 g/L. Magnetically oriented Co2Z substrates were demonstrated to exhibit a zero-field ferromagnetic resonance frequency of ~1.1 GHz that enabled device application from ultrahigh frequency (UHF) through L-band frequencies. EBG metamaterials designed and simulated on an oriented Co2Z hexaferrite substrate were compared to standard dielectric EBG designs. Results indicate that standard dielectric EBG designs, which operate over a 50% bandwidth and profile height of ~λo/10, are replaceable with an equivalent bandwidth Co2Z EBG metamaterial designed to a height of ~λo/95. The applications of the proposed metamaterial toward ultralow profile antenna designs at UHF through L-band are discussed.

Epitaxial growth of Pb(Zr0.53Ti0.47)O3 films on Pt coated magnetostrictive amorphous metallic substrates toward next generation multiferroic heterostructures

Piezoelectric films of Pb(Zr0.53Ti0.47)O3 (PZT) were deposited by pulsed laser deposition onto metallic magnetostrictive substrates. In order to optimize the growth of PZT films, a buffer layer of Pt was employed, as well as variation of deposition temperature, pressure, and laser energy. Room temperature θ-2θ x-ray diffraction measurements indicate all diffraction features correspond to reflections indexed to a single PZT phase of space group P4mm. Scanning electron microscopy images reveal pinhole-free dense films of pyramidal shaped crystal arrangements whose orientation and size were controlled by variation of oxygen pressures during deposition. The resulting PZT films had a value of d33 ∼ 46 pm/V representing a 53% increase over previous efforts to realize a piezoelectric/Metglas™ film heterostructure.

Piezoelectric properties of epitaxial Pb(Zr0.525, Ti0.475)O3 films on amorphous magnetic metal substrates

Epitaxial growth of high piezoelectric constant Pb(Zr0.525, Ti0.475)O3 (PZT) thin films deposited on amorphous magnetic Metglas® substrates by pulsed laser deposition (PLD) is reported. Particularly, Pt or Au buffer layers were employed to initiate epitaxial growth of the PZT films from atop of an amorphous surface. The optimization of deposition conditions for the PZT films with different buffer layers was systematically investigated. The crystal structure, texturing, and surface morphology of the samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Ferroelectric and piezoelectric properties were measured indicating high polarization 27 μC/cm2 and piezoelectric constant d33, 46 pm/V for the Pt buffered films. The PZT thin films grown on a magnetostrictive material have demonstrated high quality crystallographic structure and piezoelectric response, having potential for use in emerging magnetoelectric sensors.

Single crystal Fe films grown on Ge (001) substrates by magnetron sputtering

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.

Circular Polarization GPS Patch Antennas with Self-biased Magnetic Films

Magneto-dielectric substrates with thin magnetic fllms show great potential in realizing electrically small tunable antennas with improved directivity and higher bandwidth than those realized on dielectric substrates. This paper introduces self-biased magnetic fllms as a practical means to tune a patch antenna by loading a commercially available dielectric substrate. Novel antenna designs with self-biased metallic magnetic fllms and ferrite fllms were investigated. These magnetic patch antennas have improved the axial ratio from 1.57dB to 0.97dB with respect to the central frequency ranging from 1.575GHz to 1.562GHz, a large radiation frequency tunability of about 40% to 80% of the i10dB bandwidth, and a signiflcantly enhanced directivity.