Converse Magnetoelectric Composite Resonator for Sensing Small Magnetic Fields

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Magnetoelectric (ME) thin film composites utilize piezoelectric (PE) and magnetostrictive (MS) layers for passive magnetic field detection.
• Achieving high sensitivity typically requires a magnetic bias field to operate at the MS phase's maximum piezomagnetic coefficient.
• Mechanical resonances enhance the direct ME effect but limit bandwidth and DC field detection.

Purpose of the Study:

• To demonstrate converse ME modulation in mesoscopic Si cantilever composites.
• To achieve high magnetic field sensitivity, particularly for DC and low-frequency fields.
• To explore potential biomagnetic applications enabled by the novel sensor capabilities.

Main Methods:

• Fabrication of thin film Si cantilever composites (25mm x 2.45mm x 0.35mm) with piezoelectric AlN and magnetostrictive FeCoSiB layers (2µm thickness each).
• Utilizing a high-frequency mechanical resonance (approx. 515 kHz) for enhanced voltage induction.
• Employing a surrounding pickup coil with matched self-resonance for signal detection.

Main Results:

• Achieved strong induced voltages due to mechanical resonance, leading to field sensitivities up to 64 kV/T.
• Demonstrated a DC limit of detection of 210 pT/Hz^1/2.
• Obtained a sensitivity of approximately 70 pT/Hz^1/2 at 10 Hz without requiring a magnetic bias field.

Conclusions:

• The developed converse ME composites offer high sensitivity for DC and low-frequency magnetic fields.
• The absence of a bias field requirement simplifies device operation and broadens application scope.
• These findings pave the way for advanced biomagnetic sensing and measurement technologies.