Low-damping flexible Y3Fe5O12 thin films for tunable RF/microwave processors

The tunable range of RF/microwave devices is limited not only due to the difficulty in growing high-quality magnetic oxide thin films but also because of their low magnetostrictive coefficient as in Y3Fe5O12 (YIG) thin films. In this work, we have fabricated flexible YIG thin films by using pulsed laser deposition (PLD) technology, which exhibit a low-damping constant (2.67 x 10(-4)) and well-established magnetic properties suitable for RF/microwave materials. A noticeable ferromagnetic resonance (FMR) field shift of 180 Oe was obtained along the out-of-plane direction via a flexible tunable factor f(R), which results in a frequency shift as high as 550 MHz. The result shows a greater FMR tuning than that induced by ferroelectric single crystals. At the same time, a systematic theoretical framework for tuning FMR characteristics was presented for the flexible YIG/mica thin films, which would provide an effective tuning method for other flexible magnetic oxides with low magnetostrictive coefficients. Last but not least, a flexible coplanar waveguide (CPW) integrated with the flexible YIG thin films shows excellent microwave magnetic stability and fatigue-resistant behavior. It would open a new door for further applications, such as flexible spiral detectors and high-frequency signal processors in the near future.