Magnetoelectric Composite And Magnetic-field Sensor Based On Pmnt Single Crastal

The magnetoelectric effect（ME）is defined as induced electric polarization under an applied magnetic field,or conversely as induced magnetization under an applied electric field in magnetoelectric material.We can achieve the conversion of magnetic signal to electric signal by the utilization of ME,so we can apply it to the application of magnetic field sensor.The layered magnetoelectric composite is combining magnetostrictive material and piezoelectric material together,it can realize the conversion of magnetic energy and electric energy by the principle of magnetic-elastic-electric coupling,which has larger magnetoelectric coefficient than single phase magnetoelectric materials.The focus of this thesis is on the layered magnetoelectric materials and magnetic sensors fabricated based on PMNT single crystal.Nowadays,the ME magnetic sensor made by magnetoelectric materials has the ability to compete with traditional magnetic field sensors such as fluxgate and optical pump on the weak magnetic detection capability.The work I have done in this thesis is a further exploration based on the previous ones.We first establish the model of magnetoelectric response and output noise of the ME materials and ME magnetic sensor to study the method of performance optimization of ME sensor.On the study of ME materials,we fabricate the multi-layered ME composite based on the Terfenol-D alloy and PMNT single crystal,the multi-push-pull mode composite based on Metglas and PMNT single crystal,the Multi-L-T mode composite based on Metglas and Mn doped PMNT crystal,respectively.For the Multi-push-pull mode composite,we establish the dielectric loss to analyze the influences of epoxy resin on the dielectric loss of ME materials,and then we search the method to optimize the preparation process.Based on the MLT mode composite and custom-built low noise charger amplifier,we fabricate the low frequency magnetic field sensor,and the responsivity and noise equivalent magnetic induction（NEB）has been calculated and measured,which has the low NEB of 0.4pT/Hz^1/2 at 15Hz and 3pT/Hz^1/2 at 1Hz（theoretical）.Aim at the ultra-high detection sensitivity in the resonant state of ME sensor,an inductively tuned magnetic sensor is designed,which can modulate the harmonic response of sensor to the target frequency within a certain range,thus expanding the application frequency band of ME sensor.At the same time this method increases the weak magnetic detection limit of the ME sensor.For the problem that the ME sensor is susceptible to vibration interference,a unique differential working mode ME composite material is designed,which is expected to improve the adaptability of the sensor to complex environments and improve its detection accuracy.