Ultra-magnetic field sensitive magnetoelectric composite with sub-pT detection limit at low frequency enabled by flash photon annealing

Abstract

An ultra-sensitive magnetic field detector is demonstrated in a bilayer magnetoelectric (ME) composite structure employing a flash photon annealing (FPA) treated amorphous Metglas (FeBSi) alloy and piezoelectric single crystal macro fiber composites (SFC). A millisecond FPA annealing approach altered the magnetostrictive and mechanical properties of Metglas by annealing at a high temperature without inducing severe embrittlement. The ME composite (MEC) fabricated with FPA-treated Metglas (FPA-MEC) exhibited an enhanced ME coupling coefficient (at a resonance condition ~47% and at an off-resonance condition ~52%) relative to that of untreated Metglas based ME composite (pristine MEC), owing to the improved magnetic flux concentration/piezo-magnetic coefficient and reduced resonance loss in Metglas. This led to the realization of an ultra-sensitive magnetic field sensor with a direct detection limit of 0.5 pT [1 order improved performance compared to the pristine MEC (sensing limit of 5 pT)] at an extremely low resonance frequency condition (<100 Hz). The obtained results demonstrate a feasible way to design magnetic sensors for detecting bio-magnetic and extremely low-frequency (ELF) magnetic fields under ambient conditions.