  The influence of a thermal gradient on the propagation properties of
externally excited dipolar spin waves in a magnetic insulator waveguide is
investigated. It is shown that spin waves propagating towards a colder region
along the magnetization direction continuously reduce their wavelength. The
wavelength increase of a wave propagating into a hotter region was utilized to
realize its decomposition in the partial waveguide modes which are reflected at
different locations. This influence of temperature on spin-wave properties is
mainly caused by a change in the saturation magnetization and yields promising
opportunities for the manipulation of spin waves in spin-caloritronic
applications.
