Fabrication and broadband ferromagnetic resonance studies of freestanding polycrystalline yttrium iron garnet thin films

Flexible magnetic materials and devices with basic functional properties are highly desirable for flexible electronic applications in wearable products and implantable systems. In this work, a freestanding polycrystalline yttrium iron garnet (YIG) thin film with strong magnetism has been synthesized by pulsed laser deposition using a water-dissolvable Sr3Al2O6 sacrificial layer, and the magnetism of the resulting freestanding film was confirmed by a vibrating sample magnetometer and broadband ferromagnetic resonance spectroscopy. When transferred to a support layer using a thermal release tape, the flexible polycrystalline YIG thin film exhibits a lower damping constant α and larger magnetocrystalline anisotropy, in contrast to the polycrystalline heterostructure of YIG, which arises due to stress release. Thus, this work offers a viable solution for flexible YIG thin films that can be used in a number of applications.