Designing a Periodic Structure with a Composition Gradient Stack Unit to Realize a Good Comprehensive Dielectric Property of Yttrium Iron Garnet Multilayer Film

Y3Fe5O12 (YIG) thin films are highly needed in microwave devices, but the low saturation magnetization and low dielectric constant greatly limit the application of YIG thin films. It was reported that the ion substitution, for example, Pr3+, could increase the dielectric constant of Y3-xPrxFe5O12 (YPr(x)IG). Unfortunately, the dielectric loss would also be significantly increased. In this work, [YPr(0.20)IG/YPr(0.15)IG/YPr(0.10)IG](N) multilayer films were fabricated via the chemical solution deposition method, by designing a periodic structure with the [YPr(0.20)IG/YPr(0.15)IG/YPr(0.10)IG] composition gradient stack. In comparison to the average composition of YPr(0.15)IG, high saturation magnetization, high dielectric constant, and low loss were successfully simultaneously achieved in the multilayer structure. The N = 6 film exhibited a higher saturation magnetization of 252.8 emu/cm(3) than the value (213.1) of the YPr(0.15)IG (average composition) film. The dielectric constant of the N = 6 film reached 25.6 in contrast to the value of 18.3 for the YPr(0.15)IG film at 12.4 GHz, which was the contribution of the rapid flip of the electric dipole of a single-unit dielectric material and the accumulation of interface charge. Furthermore, the dielectric loss of the film with N = 6 decreased to 0.0036 compared with the value (0.0102) of the average composition film. This work demonstrated a strategy of designing a periodic structure with a composition gradient stack unit to realize a good comprehensive dielectric property through taking advantage of the multiple effects of "coherent growth, component matching, and interface accumulation".