Highly Sensitive Magnetic Sensor based on Magnetoelectric Effect and Cross-Modulation Technique

State of the art bulk magnetoelectric (ME) sensors composed of Metglas/PMN-PT fiber structures have been demonstrated to exhibit a low limit of detection (LOD) of 10 pT at 1 Hz. Because of the low cost and compact size, the ME magnetic field sensor has become competitive to other sensing technologies for applications demand for high sensitivity. The magnetic noise of ME sensors is the key parameter that results from the internal and external noise sources. To reduce the noise level, an active operation mode has been proposed. However, active ME sensors usually show a high magnetic noise over 200 pT/Hz at 1 Hz in the reports. Here, we demonstrate an ultra-sensitive ME sensors based on Metglas/PZT fiber heterostructuers operating at the complete demagnetized state of Metglas. A strong correlation was observed between the limit of detection and the degree of demagnetization of Metglas in the ME sensors, which points to a new way of improving the magnetic field sensitivity of ultra-sensitive ME sensor. Our demonstrated ME sensors based on PZT/Metglas has shown LOD below 2pT and magnetic noise level of 9.1pT/Hz^1/2 in the detection of magnetic field at 1Hz, which is one order of magnitude better than other best reported values for PZT/Metglas heterostructures.