Thermally controlled confinement of spin wave field in a magnonic YIG waveguide

•Our work demonstrates experimentally and theoretically that there is a longitudinal and transversal confinement of the spin wave magnetic field (SWMF) near the surface of a YIG film due to temperature.•We measure the electrodynamical coupling between the SWMF and an inductive probe as a function of temperature, and distance between the film and the probe.•We detect an increase in the signal induced in the probe when temperature is increased, this effect is explained as the SWMF is concentrated near the YIG-Air interface, i.e. it is confined. Methods for detecting spin waves rely on electrodynamical coupling between the spin wave dipolar field and an inductive probe. While this coupling is usually treated as constant, in this work, we experimentally and theoretically show that it is indeed temperature dependent. By measuring the spin wave magnetic field as a function of temperature of, and distance to the sample, we demonstrate that there is both a longitudinal and transversal confinement of the field near the YIG-Air interface. Our results are relevant for spin wave detection, in particular in the field of spin wave caloritronics.