| Magnetoelectric composite magnetic field sensor has ultrahigh magnetic field sensitivity, but it also meets a very serious challenge in real applications because of poor sensitivity when sensing DC and low frequency magnetic fields, large size and other issues. This thesis studied a novel magnetoelectric surface acoustic wave magnetic field sensor based on Zn O/Metglas composite multilayer films. The magnetic sensor combines layered magnetoelectric composite material with surface acoustice wave(SAW) technology. Our calculations show that very high sensitivity can be achieved even in sensing DC and broad-band AC magnetic field, and it has high temperature stability, MEMS compatibliltiy and wireless communication ability. The main work of this thesis is as follows:1. A scattering matrix method was adopted to solve the phase velocity and electomechanical coupling coefficient of Zn O/Metglas half space structure. A simple backscattering algorithm was used to determine the displacement and electric potential of the top surface. A modified coupling of modes(COM) approach was introducted which has been developed for taking into account the electrical and mechanical pertutbations caused by the periodic metal gratings on a layered substrate. Important COM parameters including equivalent velocity, reflection parameter, transduction parameter, etc were obtained. Calculation results show that the short circuit gate electrode has a larger influence on the phase velocity than the open circuit gate electrode. The phase velocity shows a maximum decrease of 0.45% at a frequency Zn O film thickness product of fhZn O=0.162GHz*μm. The mechanical load has a positive effect on the phase velocity of the Zn O/Metglas half space structure. The contribution of the reflection parameter from the electrical load is slightly smaller than that from the mechanical load. Metallization ratio has a certain effect on the amplitude of the surface acoustic wave and electrostatic energy storage.2. A mathematical model was proposed to simulate the magnetic properties of an amorphous magnetic ribbon that has been field-annealed in the ribbon plane at arbitrary angle. The dependences of magnetization, engineering magnetiostirction and Young’s modulus were derived as functions of the applied field. Field annealing experiments were then performed on selected Metglas2605SA1 ribbons. The best results were obtained in the sample annealed at 360 oC for one hour. The field dependent Young’s modulus and magnetomechanical coupling of the as casted amorphous ribbons and the field annealed samples were then measured by a resonance/antiresonance method. The results show that field annealing altered the stress state of Metglas ribbons, and the electromechanical coupling coefficient(k33) along the easy axis increased after the magnetic field annealing. The k33 reached 0.32, two times of the value of as-cased ribbon, upon applying a bias magnetic field of 8Oe. The DE effect curves measured along the easy and hard axis are consistent with the simulated ones by the mathematical model. The k33 measured along the hard axis is slightly lower than that measured along the easy axis. The measured Young’s modulus first decreased then increased with the applied magnetic field, and the highest ΔE effect value was 53.3%.3. Highly c-axis oriented Zn O film was successfully deposited on the polishing Metglas amorphous ribbon using magnetron sputtering after adjusting the experimental conditions. The full width at half maximum of the(002) rocking curve is only 3.5 degreee. The surface roughness is 2 nm. Fianlly, aluminum interdigital transducer was prepared using microfabrication technology, and the center frequency and insertion loss were measured by a vector network analyzer. The test result show that the center frequency is close to the designed one, but the insertion loss is high. |
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