Northeastern University

Other

Metamagnetics, Inc.

Carmine Vittoria

Hoton How

Vincent G Harris

Anton L Geiler

Paul M Zavracky

Nicol E McGruer

Steven A Oliver

Ta-Ming Fang

Khabat Ebnabbasi

Allan Widom

Yizhou Huang

A method of making a ferrite thin film is provided in which a portion of the iron ions in the ferrite are substituted by ions of at least one other metal. The substituting ions occupy both tetrahedral and octahedral sites in the unit cell of the ferrite crystal. The method includes placing each of a plurality of targets, one at a time, in close proximity to a substrate in a defined sequence; ablating the target thus placed using laser pulses, thereby causing ions from the target to deposit on the substrate; repeating these steps, thereby generating a film; and annealing the film in the presence of oxygen. The plurality of targets, the sequence of their ablation, and the number of laser pulses that each target is subjected to, are selected so as to allow the substituting ions to occupy both tetrahedral and octahedral sites in the unit cell.

Method of engineering single phase magnetoelectric hexaferrite films

An apparatus and method, directed to measuring permeability of a magnetoelectric sample, are described. The apparatus includes a sample holder configured to present the magnetoelectric sample to a permeability analyzer for measurement of the sample's permeability, and to facilitate application of a DC voltage to the sample in a way that isolates the DC voltage from the permeability analyzer. The described apparatus and method may be used to measure the permeability values associated with the magnetoelectric sample with respect to a range of DC voltages applied to the sample, while protecting the measuring instrumentality from damage from the applied DC voltages.

Apparatus and method of measuring permeability of a sample across which a DC voltage is being applied

Tunable microwave magnetic devices that provide increased performance with reduced size, weight, and cost. The disclosed microwave magnetic devices are voltage-tunable devices that include ferrite substrates. To tune the devices, the magnetic permeability of the respective ferrite substrates is varied by external, voltage-tuned, magnetic fringe fields created by one or more magnetoelectric (ME) transducers.

Voltage tuning of microwave magnetic devices using magnetoelectric transducers

A broadband integrated circulator antenna (BICA) module for receiving and transmitting signals with high efficiency and high gain. The BICA can have a bandwidth of over 70% of a radar band and can operate in frequencies from UHF to S-band and above. The BICA has a stack configuration that includes a low profile antenna, a reflecting layer or a metamaterial substrate layer, and a circulator. The circulator is placed proximal to antenna, which greatly reduces the size of the BICA. The circulator can be a stripline Y-junction ferrite circulator and the antenna can be a coaxial center fed bow-tie antenna. The reflecting layer or metamaterial substrate layer can comprise electronic bandgap metamaterial and a high permeability ferrite substrate. The high permeability ferrite substrate can be cobalt substituted Z-type barium hexaferrite.

Antenna module having reduced size, high gain, and increased power efficiency

Disclosed is a method for improving the sensitivity of a fluxgate magnetometer for which high-order harmonics are detected and utilized in determining a weak external magnetic field expressed in the core region. These harmonic signals are processed coherently so as to increase the signal-to-noise ratio, since noise can only add to the signal incoherently at these harmonic frequencies. Also disclosed is a method for improving the sensitivity of a fluxgate magnetometer for which the technique of waveform autocorrelation is used in determining a weak external magnetic field expressed in the core region. By convolving the gated signal with a waveform duplicating the signal itself, noise content is effectively suppressed, thereby increasing the resolution power of the fluxgate magnetometer.

Fluxgate signal detection employing high-order waveform autocorrelation

A method for the fabrication complex-transition metal oxide (CTMO)/semiconductor or dielectric substrate integrated devices includes the separation of the CTMO film growth process from the CTMO-film/semiconductor or dielectric substrate integration process. The CTMO-film is transferred from the native substrate to the final substrate for fabrication into devices. The CTMO-film is grown onto a native substrate under growth conditions chosen to provide a CTMO-film having desirable properties and thickness. No restrictions are placed upon the native substrate used, the growth method used, or on the growth conditions required. The CTMO-film is then joined to the semiconductor or dielectric substrate and the native substrate is removed, providing the basis for an integrated electronics, photonics, or MEMS device. Techniques fully compatible with semiconductor processing can be used to fabricate monolithically integrated CTMO/semiconductor devices in a first embodiment.

Method of fabricating an integrated complex-transition metal oxide device

A magnetic/acoustic transducer is disclosed. The transducer can be used in security/smart tag applications. The transducer includes a sensor tag made of magnetic metallic glass having a relatively high magnetostriction and a relatively low coercivity. Driving signals are provided by an rf dipole loop antenna. The tag responds to the rf signals and converts the exciting magnetic field into acoustic signals via magnetoelastic coupling. That is, the tag is forced to vibrate in unison with the incident electromagnetic signals generating longitudinal acoustic waves along a length of the tag. This results in radiation of ultrasound waves in air which can then be detected and characterized using an ultrasound microphone or a piezoelectric sensor. The tag is provided having a length equal to one half or one quarter long of an acoustic wavelength so that an acoustic resonance condition is established to maximize the generation of ultrasound waves in air. The measured ultrasound signal is locked in phase with the excitation or reference signal for sensitive long-range detection. The tag can operate in a magnetized or a demagnetized state to stimulate binary signals for security-tag applications. Tags of different length and/or geometry can be deployed in combination so that the tag transducer produces unique and distinguishable frequency spectrums to be used as smart tags.

Method and apparatus for generating and detecting acoustic signals

The present invention discloses a frequency tunable filter which includes an electromagnetic (E-M) wave propagation line which includes a microstrip and a ground plane in the substrate for transmitting a sequence of E-M signals via the propagation line. The E-M wave propagation line includes a frequency tuning mechanism, i.e., the magnetic layer, which is capable of utilizing a ferromagnetic anti-resonance frequency response to the E-M signals transmitted via the propagation line for controlling and frequency tuning the E-M signal transmission. In one of the preferred embodiments, the E-M wave propagation line includes a microstrip forming on the top surface of a dielectric or semiconductor substrate for receiving and transmitting the E-M signals and a ground plane forming on the bottom surface of the semiconductor substrate. And, the frequency tuning mechanism includes a ferromagnetic layer formed in the substrate between the microstrip and the ground plane.

Tunable millimeter wave filter using ferromagnetic metal films

An array antenna includes a ferrite substrate having a two-dimensional planar array of antenna elements disposed over a first surface thereof and means for applying an external magnetic field having a magnitude and direction which can be varied at least in a plane in which the antenna elements lie. The amplitude and direction of the external magnetic biasing field is varied to control the relative phases between each of the plurality of antenna elements and to steer the direction of a main antenna beam in two dimensions.

Antenna array having two dimensional beam steering

A planar SQUID magnetometer for detection and measurement of an applied magnetic flux is disclosed wherein a planar microwave-resonant element overlaps a Josephson device incorporated in a high-T.sub.c superconducting, thin-film SQUID device, thereby providing inductive coupling between the planar microwave-resonant element and the SQUID device. When the microwave-resonant element is excited by incident high-frequency microwave radiation, the intensity of reflected microwave radiation varies in response to a magnetic flux applied to the SQUID device in accordance with non-linear oscillatory behavior of the microwave-resonant element due to inductive loading by the SQUID device. The microwave-resonant element and the SQUID device are preferably fabricated photolithographically on a single substrate.

Planar squid magnetometer with inductively coupled microstrip resonator

A microstrip antenna includes a ferrite loaded substrate having a ground plane conductor disposed over a first surface thereof and having a strip conductor disposed over a second surface thereof. A DC magnetic field biasing circuit provides a directed DC magnetic field to the ferrite substrate such that the strip conductor radiates electromagnetic energy having circular polarization. In one embodiment, a ferrite material is disposed over the strip conductor to reduce the radar cross section of the antenna.

Ferrite microstrip antenna

A method is provided for fabricating a thin film of ferrite material upon a variety of substrates wherein pulsed high power laser light impinges upon a target of ferrite material causing localized vaporization of the ferrite material and subsequent deposition upon a proximate substrate. The rapidity with which the target material is vaporized promotes chemical stability during ferrite film growth. Both the target and the substrate are maintained inside a vacuum chamber, and are maintained substantially within a temperature range of 550.degree.-900.degree. C. The equipment needed to practice the method is relatively inexpensive. Furthermore, the method allows for the large-scale production of high quality ferrite films with preferential magnetic texture, wherein the magnetization of the ferrite material aligns in a preferred direction in the plane of the film.

Fabrication of ferrite films using laser deposition

A method is provided for fabricating a thin film of ferrite material upon a variety of substrates wherein pulsed high power laser light impinges upon a target of ferrite material causing localized vaporization of the ferrite material and subsequent deposition upon a proximate substrate. The rapidity with which the target material is vaporized promotes chemical stability during ferrite film growth. Both the target and the substrate are maintained inside a vacuum chamber, and are maintained substantially within a temperature range of 550.degree.-600.degree. C. The equipment needed to practice the method is relatively inexpensive. Furthermore, the method allows for the large-scale production of high quality ferrite films with preferential magnetic texture, wherein the magnetization of the ferrite material aligns in a preferred direction in the plane of the film.

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Boston, MA, United States of America

Carmine Vittoria