Giant sensitivity to magnetic field variation in the spin wave interferometer based on the system of exchange-coupled films of yttrium iron garnet

Abstract

In this work, we present experimental data on the interference of backward volume magnetostatic wave (BVMSW) counter-propagating in the structure with two exchange-coupled yttrium iron garnet layers. The layers are engineered to have different saturation magnetization that gives a possibility to BVMSW resonantly interacting with exchange modes of the two-layer structure. The BVMSW is excited by two antennas placed on top of the structure, while the third one placed between them is used for the detection of inductive voltage V generated by waves superposition. It is shown that maximal changes of the output inductive signal δV with the variation of magnetic field δH occur if, first, the waves interfere destructively and, second, the frequency corresponds to the resonant interaction of BVMSW with the exchange waves. In this case, obtained data reveal large sensitivity S = δV/δH approaching S ≈ 267 dB/Oe in the vicinity ±0.1 Oe of the resonant field H. The observed high sensitivity is of great importance for the development of compact sensitive magnetometers operating at room temperature.