Femtosecond laser-patterned magnetic anisotropy enables self-biased magnetoelectric sensors with ultra-sensitive angle detection

Among various magnetic sensors, magnetoelectric sensors offer significant advantages in weak magnetic field detection due to their exceptional sensitivity, operational convenience, and promising potential for miniaturization and low cost. However, their practical application is limited by the requirement for an external DC bias field and the insufficient sensitivity to in-plane AC magnetic fields. In this work, straight-line structures oriented at angles of 0°, 45°, and 90° relative to the sample width direction are fabricated on the surface of the Metglas magnetostrictive material using femtosecond laser technology, resulting in a built-in bias magnetic field (0.65 Oe) in the magnetoelectric sensor. This built-in bias field originates from the laser-annealing-induced magnetic anisotropy, where the laser-patterned structures produce a preferred orientation for the magnetic moments. This anisotropy is confirmed by analyzing the magnetic domain structures and the measured magnetization curves, which showed a clear dependence on the orientation of the laser-induced patterns. Operating without external DC bias field, the magnetoelectric sensor yields a high magnetoelectric coefficient of 96.8 V·cm⁻¹ ·Oe⁻¹ , an ultra-low detection limit of 2.5 pT, and distinguishable angular increments of 0.03°. This unique combination of self-bias operation and high performance, enabled by the femtosecond-laser-induced magnetic anisotropy, makes our sensor a highly promising candidate for energy-efficient magnetic sensors and precision navigation systems.