Soft Magnetism and Microwave Properties of FeCoSiB Ferromagnetic Alloys Grown on AlN and AlScN Thin Films

Thin-film magneto-electric composites based on aluminum nitride (AIN) and Sc-doped AlN exhibit great potential for applications in magneto-electric devices. In this letter, we report soft magnetism and microwave properties in FeCoSiB ferromagnetic alloys grown on AlN and AlScN thin films. According to the hysteresis loop, the coercive fields for FeCoSiB/AlN/Mo/Si and FeCoSiB/AlScN/Mo/Si are 43 and 107 Oe, respectively. The influence of interfacial state on magnetic damping is investigated by measuring the magnetic dynamic properties. Scanning electron microscope images show that AlScN film has a larger grain size and rougher surface than that of AlN. The effective magnetization and damping factors are obtained from the ferromagnetic resonance spectroscopy. The damping factor of the magneto-electric heterojunction on AlN/Mo/Si is an order of magnitude higher than that on Si, indicating the interfacial conditions of thin film stacks affect the magnetic dynamic properties. Our findings indicate that the growth quality of piezoelectric materials has a significant impact on magneto-electric films with low-loss tangents at radio-frequency (RF)/microwave frequencies. This work is of practical importance for developing future RF/microwave magneto-electric devices.