title: Sensitivity Enhancement in Magnetic Sensors Based on Ferroelectric-Bimorphs and Multiferroic Composites.
abstract: Multiferroic composites with ferromagnetic and ferroelectric phases have been studied in recent years for use as sensors of AC and DC magnetic fields. Their operation is based on magneto-electric (ME) coupling between the electric and magnetic subsystems and is mediated by mechanical strain. Such sensors for AC magnetic fields require a bias magnetic field to achieve pT-sensitivity. Novel magnetic sensors with a permanent magnet proof mass, either on a ferroelectric bimorph or a ferromagnetic-ferroelectric composite, are discussed. In both types, the interaction between the applied AC magnetic field and remnant magnetization of the magnet results in a mechanical strain and a voltage response in the ferroelectric. Our studies have been performed on sensors with a Nd-Fe-B permanent magnet proof mass on (i) a bimorph of oppositely-poled lead zirconate titanate (PZT) platelets and (ii) a layered multiferroic composite of PZT-Metglas-Ni. The sensors have been characterized in terms of sensitivity and equivalent magnetic noise N. Noise N in both type of sensors is on the order of 200 pT/√Hz at 1 Hz, a factor of 10 improvement compared to multiferroic sensors without a proof mass. When the AC magnetic field is applied at the bending resonance for the bimorph, the measured N ≈ 700 pT/√Hz. We discuss models based on magneto-electro-mechanical coupling at low frequency and bending resonance in the sensors and theoretical estimates of ME voltage coefficients are in very good agreement with the data.
authors.affiliation: Physics Department, Oakland University, Rochester, MI 48309, USA. sreeni@vt.edu.
authors.forename: Gollapudi
authors.initials: G
authors.lastname: Sreenivasulu
authors.affiliation: Electrical and Computer Engineering Department, Oakland University, Rochester, MI 48309, USA. pqu@oakland.edu.
authors.forename: Peng
authors.initials: P
authors.lastname: Qu
authors.affiliation: Institute for Information Systems, Novgorod State University, Veiky Novgorod 173003, Russia. vladimir.petrov@novsu.ru.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Petrov
authors.affiliation: Electrical and Computer Engineering Department, Oakland University, Rochester, MI 48309, USA. qu2@oakland.edu.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Qu
authors.affiliation: Physics Department, Oakland University, Rochester, MI 48309, USA. srinivas@oakland.edu.
authors.forename: Gopalan
authors.initials: G
authors.lastname: Srinivasan
keywords: bending resonance; bimorph; ferroelectric; magnetic sensor; multiferroic; permanent magnet; piezoelectric; proof mass