Magnetic Field Sensor Based On Magnetoelectric Effect And Relaxor Ferroelectric Single Crystal

The magnetoelectric(ME)effect is characterized by the response of electrical polarization in material to an applied magnetic field,or conversely the magnetization response in material to an applied electric field.Based on ME effect,ME materials can realize the conversion between magnetic energy and electric energy,which have a great potential in sensors,transducers,microwave devices and information storage.Combining magnetostrictive material and piezoelectric material together,the ME composite obtained shows huge ME effect.ME magnetic sensors is consisted of ME composite,converting magnetic signal into electric signal,and pre-amplifier,amplifying small electric signal.The focus of this thesis is on the fabrication of ME magnetic sensor with low magnetic detection limitation based on relaxor ferroelectric single crystal.We firstly model the equivalent circuit,ME response and intrinsic electrical noise of ME magnetic sensor,laying the foundation for the improvement of ME response and the reduction of electrical noise.In order to obtain a great ME response,Metglas of high piezomagnetic coefficient and relaxor ferroelectric single crystal PMNT of high piezoelectric constant are taken as magnetostrictive material and piezoelectric material respectively.We optimize the polarization condition of Push-Pull ME composite and destroy during polarization is avoided.Then the size of magnetostrictive material is optimized as well,and the ME response is improved consequently.To lower the dielectric loss of core composite,the newly Multi-L-L ME composite is fabricated.We finally design Multi-L-T ME composite,which shows the best performance with high ME response and low dielectric loss.The noise equivalent magnetic induction of Multi-L-T composite is as low as1.9 p T/Hz1/2@ 1Hz.We fabricate a charge amplifier with ultralow electrical noise.The amplifier is then packaged with ME composite and the complete ME magnetic sensor is obtained.The range,sensitivity,linearity,bandwidth and intrinsic noise of this ME sensor are characterized.The magnetic detection limitation of 2.8 p T/Hz1/2@ 1Hz is obviously lower than that of fluxgate.At last,the triaxial magnetic sensor based on single-axis ME magnetic sensor is assembled.Due to the merits like low noise,low cost,low power consumption,small size,vector and working at room temperature,ME magnetic sensor will hopefully replace the traditional magnetic sensor like fluxgate and optically pumped magnetometer.