Saba Zare

Effects of cobalt substitutions on the magnetoelectric coupling of M-type hexaferrite films

We have experimentally investigated the correlation between the magnetoelectric coupling α and Co substitutions in M-type hexaferrite films. Specifically, the following family of M-type hexaferrites materials were investigated Sr2+Cox2+Ti3−0.5x4+Fe83+O192−, where x varied from 1.2 to 3.5. The parameter α was measured for the cases (a) the induced magnetization was perpendicular, α⊥, and (b) parallel, α∥, to the applied electric field. A maximum value of α⊥ = 1.01 × 10−8 sec/m was measured for x = 1.65. This optimum value may be related to the maximum packing density of cobalt ions in octahedral sites and still maintain charge neutrality. Also, α∥ reached a minimum value of 2.51 × 10−10 sec/m for x = 1.9.

Magnetoelectric sensor excitations in hexaferrite films

We developed techniques for H- and E-field sensors utilizing single phase magnetoelectric (ME) hexaferrite thin films in the frequency range of 1 kHz to 10 MHz. The technique incorporating solenoid coils and multi-capacitors bank was developed to probe the physics and properties of ME hexaferrite film and explore ME effects for sensor detections and tunable device applications. For H-field sensing, we obtained sensitivity of 4 × 10−4 V/Gm and for E-field sensing the sensitivity was 10−3 Gm/V. Tunability of up to 6% was achieved for tunable inductor applications. The proposed fabrication designs lend themselves to significant (∼106) improvements in sensitivity and tunability.

Magnetoelectric sensor excitations in hexaferrite slabs

We developed techniques for H- and E-field sensors utilizing single phase magnetoelectric (ME) hexaferrite slabs in the frequency range of 100 Hz to 10 MHz. Novel circuit designs incorporating both spiral and solenoid coils and single and multi-capacitor banks were developed to probe the physics and properties of ME hexaferrites and explore ME effects for sensor detections. Fundamental measurements of the anisotropic tensor elements of the magneto-electric coupling parameter were performed using these novel techniques. In addition, for H-field sensing experiments we measured sensitivity of about 3000 Vm−1/G using solenoid coils and 8000 Vm−1/G using spiral coils. For E-field, sensing the sensitivity was 10−4 G/Vm−1 and using single capacitor detector. Sensitivity for multi-capacitor detectors was measured to be in the order of 10−3 G/Vm−1 and frequency dependent exhibiting a maximum value at ∼1 MHz. Tunability of 0.1%–90% was achieved for tunable inductor applications using both single and multi-capacitor...

Field Sensors and Tunable Devices Using Magnetoelectric Hexaferrite on Silicon Substrates

In this paper, the H-field and E-field sensors as well as the tunable devices are fabricated by utilizing single-phase magnetoelectric (ME) hexaferrite thin films on a silicon substrate. A buffer layer of indium-tin oxide is introduced between the Si wafer and the ME film. The required voltage excitations are reduced to values below 1 V at room temperature, hence making these devices compatible with planar integrated circuits (ICs) and CMOS. A planar spiral coil is utilized in a frequency range of 100 Hz to 10 MHz for sensing applications by applying an ac field (electric or magnetic) for excitation of the ME film. For H-field (E-field) sensing, a sensitivity of up to 1000 Vm-1/G (10-7 G/Vm-1) is attained. The corresponding sensitivity for H-field is 4 × 104 up to 107 V/T for 3 kHz up to 10 MHz. Tunability of up to 60% is achieved for tunable inductor applications; moreover, a change of 26% in voltage is observed at a single frequency by applying a voltage of 3 V on the ME film, thus performing as a single frequency detector. The proposed devices are made of single-phase materials, so they are simple to fabricate and capable to operate at the voltages of few volts; these features make them viable as a new generation of the ME devices for integration in ICs.

Power-efficient voltage tunable RF integrated magnetoelectric inductors with FeGaB/Al 2 O 3 multilayer films

This work reports new integrated GHz magnetic inductors based on solenoid structures with FeGaB/Al2O3 multilayer films, which show significantly enhanced inductance and quality factor at GHz frequencies over their air core counterparts. These inductors show excellent high-frequency performance with a wide operation frequency range of DC-2.5GHz, in which the inductance of the integrated magnetic inductors show >100% enhancement compared with that of the same size air core inductor. Voltage tunable magnetoelectric inductors were fabricated with MEMS processing by putting these inductors on 0.5mm thick ferroelectric (011) cut lead magnesium niobate - lead titanate PMN-PT slab, which showed a voltage tunable inductance of >100%. These novel voltage tunable GHz inductors with giant tunable inductance show great promise for applications in radio frequency integrated circuits.

Frequency Response of a Coupled Magnetoelectric Hexaferrite Film on a Spiral Coil

This letter presents an experimental assessment and evaluation of the frequency response of a recently proposed magneto-electric (ME) device (suitable for H- and E -field sensor and tuning applications). The device is fabricated by incorporating a single-phase ME hexaferrite thin film on a silicon substrate, which is able to operate at a few volts. A conductive buffer layer of indium tin oxide is introduced between the Si substrate and the ME film to accommodate the voltage reduction for ME film excitation at room temperature. A planar spiral coil is then utilized for application or detection of an ac magnetic field by excitation of the ME film or change in magnetization as a flux, respectively. Through a nonlinear experiment, the frequency of the signals for both spiral coil and ME film is changed in the range of 1–10 MHz. The voltage across the coil is then measured as a function of the two sources with coupled frequencies. Coupling is, therefore, related to the frequency and amplitude of both these signals. The frequency response in these experiments provides a better understanding of the ME effect coupling. Experimental data confirm these findings.

Magneto-Electric Effect Modeled in a Nonlinear Experiment

This letter presents a nonlinear model and experimental assessment of a magneto-electric (ME) device fabricated using a hexaferrite film and a spiral coil. In both the model and experiment, two sources are applied to the ME film and the spiral coil. The ME effect is modeled by two equation-based sources for generating the ME effect from the ME film to the spiral coil (and vice versa). A simple equivalent circuit model is used. In the nonlinear experiment, the two different sources are applied in a frequency range of 1–40 MHz. The voltage across the coil is measured as a function of the two sources with coupled frequencies and amplitude. In the simulation, the voltage on the spiral coil is a combination of the two sources modulated in the frequency domain; moreover, they are in agreement with experimental results showing that the output voltage of the spiral coil is a function of not only its direct source, but also the source on the ME film (so arising from the ME coupling). Between the experiment and simulation, the average amplitude difference is approximately 20%, whereas the resonance peaks are in agreement.

Deposition of Magnetoelectric Ferrite Thin Films Using Multiple Targets Technique

The magnetoelectric (ME) effect has been detected in cobalt-doped M-type hexaferrite bulk. We have demonstrated that the hexaferrite films of the M-type exhibiting the ME effect can be deposited from single targets as well as multiple targets as in the alternating target laser ablation deposition technique. The corresponding ME coupling is sufficiently high at room temperature to allow for potential device applications α = 5.2 × 10-9 m/s. The saturation magnetization value (4π Ms) of the film was measured to be 2000 G, consistent with a vibrating sample magnetometer and the ferromagnetic resonance measurement.

Room Temperature Sensing of Magnetic Fields Using Magnetoelectric Thin Films

We present the design, characterization, and fabrication of a sensing device for measuring low-frequency ac magnetic field variations using a single-phase magnetoelectric (ME) thin film. This ME device is fabricated using SrCo2Ti2Fe8O19 and deposited on a 500-nm-thick Indium Tin Oxide layer. The ME film is then deposited on a silicon substrate using a pulsed laser deposition technique. The device size (volume) is 0.02 cm3, and its overall power consumption is 14W. We also show that this sensing device can be used to detect low ac and dc magnetic fields. In this experiment, we employ a modified Wheatstone bridge circuit as an alternative approach to detect the change in capacitance of the ME film when an external field

Deposition of magnetoelectric hexaferrite thin films on substrates of silicon

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