Pushing the detection limit of thin film magnetoelectric heterostructures
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ebastian Salzer Institute of Electrical and Information Engineering, Kiel University, Kiel 24143, Germany
Necdet O. Urs Institute for Materials Science, Kiel University, Kiel 24143, Germany
Jens Reermann Institute of Electrical and Information Engineering, Kiel University, Kiel 24143, Germany
Erdem Yarar, André Piorra, Christine Kirchhof, and Enno Lage Institute for Materials Science, Kiel University, Kiel 24143, Germany
Michael Höft, Gerhard U. Schmidt, and Reinhard Knöchel Institute of Electrical and Information Engineering, Kiel University, Kiel 24143, Germany
Jeffrey McCord, Eckhard Quandt, and Dirk Meynersa) Institute for Materials Science, Kiel University, Kiel 24143, Germany (Received 10 June 2016; accepted 1 February 2017)
Composite magnetoelectrics implemented as thin film heterostructures are discussed in view of their applicability as highly sensitive magnetic field sensors. Here, either PZT or AlN served as piezoelectric component. The magnetostrictive phase consisted of layer systems based on FeCo or (Fe90Co10)78Si12B10. All functional layers were deposited with thicknesses of a few micrometers on Si cantilever structures with typical lateral dimensions of 25 mm by 2.2 mm. Magnetoelectric coefficients as large as 6900 V/cm Oe and a limit of detection as low as 1 pT/(Hz)1/2 were measured. Currently, the best result demonstrates a detection limit of 500 fT/(Hz)1/2 at 958 Hz frequency using a set of two sensors for external noise suppression. A frequency conversion technique is proposed to broaden the applicability of resonant magnetoelectric sensors to a wider frequency range. Finally, the achieved sensor performance is evaluated with regard to typical magnetic field amplitudes in medical applications.
I. INTRODUCTION
Composite magnetoelectric (ME) materials combine a magnetostrictive phase and a piezoelectric phase to a ME heterostructure. As in single phase ME materials, the electric properties can be manipulated using an externally applied magnetic field and, vice versa, the magnetic properties using an electric field.1 This coupling of properties is very interesting, because of the potential for application in multifunctional or highly sensitive devices. Provided that the incorporated materials and processes are compatible, magnetostrictive, and piezoelectric materials can be chosen for the fabrication of ME heterostructures so as to be attuned to the particular application under consideration. Thus, the current limitation of single phase ME materials with regard to Contributing Editor: Michael E. McHenry a) Address all correspondence to this author. e-mail: [email protected] This paper has been selected as an Invited Feature Paper. DOI: 10.1557/jmr.2017.58
magnitude and temperature dependence of the magnetoelectric effect can be circumvented.1 A thin film approach to layered ME composites additionally increases design flexibility2–4 and enables the exploitation of coupling phenomena such as exchange biasing of the magnetostrictive layers,5 which further increases the usability of the resulting ME dev
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