A Magnetoelectric Compass for In-Plane AC Magnetic Field Detection

Magnetoelectric (ME) composites exhibit high sensitivity for detecting the strength of weak magnetic field. Yet, they are not sensitive to the angle of a randomly orientated in-plane ac magnetic field, since the strain-mediated ME structures merely response to magnetic field along certain direction. In this article, an ME compass for detecting the intensity as well as the orientation of in-plane ac magnetic field is proposed. The ME compass is designed with the barbell-shaped structure, where NdFeB permanent magnets induce compressive stress on piezoelectric components via torque effect, so that the magneto-mechano-electric coupling effect is mediated by stress without dc magnetic bias field. The ME compass reveals a low resonant frequency (<50 Hz) that is favorable for practical applications. The contribution from d33 piezoelectric coefficient is dominant to the ME effect of the compass, with an ME coefficient of 0.7302 V/cm Oe at resonance. The proposed device presents excellent performance for detecting in-plane ac magnetic field with arbitrary direction, where the sensitivities for intensity and angle are 0.01 Oe and ±0.2°, respectively. Additionally, the barbell-shaped structure brings advantages, such as simple construction, stable performance, and durability, indicating promising applications in angular sensors and compasses.