Study On Magnetic Field Modulation Of Magnetoelectric Heterostructures And Magnetic Sensor

Magnetoelectric(ME)materials,existing rich underlying physics and protential application in multi-functional electronic devices,are extensively studied from materials,physics and information technologies in recent years.A novel magnetic sensor based on these ME composite materials,is expected to break the market dominance of traditional magnetic sensorssuch as Superconducting Quantum Interferometer,Fluxgate and Hall probe,due to its advantages of high sensitivity,small volume,low cost and low power consumption.Then,it can be widely used in medical detection,intelligent transportation,national defense,wireless sensor network,etc.The magnetic sensors are generally used in the range of mHz-Hz,so the detection sensitivity at low frequencies is especially important.The sensitivity of magnetic sensor at low frequencies is mainly limitted by the intrinsic noise and environmental vibration noise.With regards to noise reduction,in this thesis,we focus on two strategies:working mode and structure/package design.First,we employ magnetic field modulation method to avoid 1/f noise at low frequency range,then,we designed curve-shaped ME structure and found that the optimized structure has a notable capability to reduce the vibration noise.Various PMN-PT/Metglas and PZT/Metglas multi-push-pull mode,PIN-PMN-PT/Metglas L-T mode ME composites have been fabricated.This thesis is mainly divided into the following three parts:1.The PIN-PMN-PT/Metglas L-T mode ME composite and PIN-PMN-PT/Metglas L-T mode ME composite have been characterizated with regards to passive detection and active detection(or magetic field modulation),respectively.In detail,the influence of the bias magnetic field,frequency and amplititue of the magnetic field to the ME properties for these two detection modes were investigated.Morever,we measured the detection sensitivity under different detection modes and their performance in response vibration noise.The detection sensitivity obtained by active detection are lower than passive detection under weak-vibration environment,but under strong-vibration environment,the sensor under active detection mode have weaker ME singal,but much lower vibration noise that under passive mode.Thus,active detection mode has notable advantage to use in real-world environment.2.For the PZT/Metglas multi-push-pull mode ME composite,the curve-shaped sensor has slight decrease in ME coefficient relative to the plane-shaped one(?16 V/(cm·Oe))·However,the vibration-induced noise of curve-shaped sensor is significantly reduced.Consequently,the signal-to-noise ratio and detection sensitivity are improved via the structure design.Furthermore,we found that vibration noise are dependent on the curvature of ME heterostructure,i.e.,the smaller curvature radius of the ME composite structure,the smaller the noise caused by the vibration.3.The package optimization is another efficient approach to reduce the vibration noise and enhance the detection sensitivity.PZT/Metglas multi-push-pull mode ME composites under mechanical clamping state,have lower ME coefficient(13 V/(cm-Oe)vs 21 V(cm·Oe)),but exhibit much greater reduction in vibration-induced noise.As as result,the equivalent magnetic noise is reduced in all.Thus,the detection sensitivity has been significantly improved by mechanical clamping package.In summary,we prepared the magnetoelectric heterostructures which have high detection sensitivity.In order to optimize the performance and use under the real application environment,we proposed magnetic field modulation and packaging process,which have important reference value.