Nonreciprocal Spin Wave Propagation in a Thin YIG Film for an in-Plane Magnetization*

We report measurements on the magnetic field dependence of the wavevector of spin waves of a given frequency propagating in a 3μm YIG film for an in-plane magnetic field. Waves are transmitted and received from opposing but parallel edges of a rectangular platelet using 50μm wire antennas adjacent to the edges and detected using a phase-sensitive method. Both the Damon-Eshbach (DE) and backward volume (BV) modes are observed, together with their dependence on the in-plane magnetic field direction, as measured relative to the propagation direction. Measurements are performed in a variety of configurations including YIG/GGG, Cu/Air/YIG/GGG, Cu/YIG/GGG, and Pt/YIG/GGG and are performed for both positive and negative fields and for forward and backward propagation relative to a given field direction. Data are fully reproduced only when both the magnetic field and the propagation direction (the wavevector) are reversed (double reversal); data obtained when only one of these (field or wavevector) is reversed generally do not reproduce. The difference is largest for the DE mode, in agreement with earlier theoretical predictions.