Development of nanocrystallized magnetoelastic sensors with self-biased effect and improved mass sensitivity

• Positive impact of the crystallization in the magnetoelastic sensors performance; • Crystallization of magnetoelastic sensors via annealing increases the frequency and the quality factor of the resonance; • Magnetoelastic sensor annealed at 550 °C presents a self-biased resonance; • The sensitivity of the crystallized magnetoelastic sensor is a 40 % higher than the as-quenched one. The growing demand for cost-effective and wireless sensing technologies requires the development of simple, efficient and optimized sensors able to accurately detecting external agents. Magnetoelastic resonators represent an alternative to the traditional sensing systems, able to combine all the previously cited factors. Several studies have focused on increasing their sensitivity, in order to make it closer to the market. The present study explores thermal treatments as a novel approach to enhance the sensitivity of magnetoelastic resonators, focusing on the positive impact of crystallization processes induced in magnetoelastic platforms. The experimental results confirm an enhancement of resonant frequency and quality factor of the magnetoelastic platforms as treatment temperature increases. Particularly, the sensor annealed at 550°C shows an increase of the resonant frequency value of 45 % with respect to the as-quenched platform, being that increase of around 1700 % for the quality factor. In addition, the nanocrystallization induction leads to a self-biased resonance, consequence of the intrinsic magnetization resulting from the crystallization in Fe 2 B and FeCo phases. Further, the study shows the importance of stability in resonant frequency, emphasizing the potential of the 550°C-annealed platform for mass sensor applications. Gold deposition experiments reveal the enhanced sensitivity of the sensor annealed at 550°C of 40 % compared to the as-quenched sensor, as well as an increase of 38 % on its accuracy. These findings represent a significant step forward in the development of magnetoelastic-based mass sensors, highlighting the pivotal role of thermal treatments in optimizing sensitivity for practical and efficient external agents detection systems.