Freestanding single-crystal Ni0.5Zn0.5Fe2O4 ferrite membranes with controllable enhanced magnetic properties for flexible RF/microwave applications

Flexible epitaxial ferrite thin films are crucial for flexible RF/microwave devices; however, they are difficult to be fabricated due to critical growth conditions. In this work, we demonstrate a water-dissolvent process to obtain high-quality freestanding single-crystal NiZn-spinel ferrites. By utilizing their high flexibility, significant mechanical tuning of magnetic properties in flexible NZFO epitaxial thin films has been achieved, which is much greater than those of traditional multiferroic heterostructures using rigid substrates. A giant FMR field shift of 2027 Oe was achieved with the contribution of the two magnon scattering effect, where the spin-wave propagation is sensitive to lattice deformation, and spin-spin interactions can be manipulated easily via strain/stress conditions. The result indicates that the freestanding epitaxial ferrite thin films will be widely used in flexible RF/microwave applications in the future.