  Thermal spin pumping constitutes a novel mechanism for generation of spin
currents; however their weak intensity constitutes a major roadblock for its
usefulness. We report a phenomenon that produces a huge spin current in the
central region of a multilayer system, resulting in a giant spin Seebeck effect
in a structure formed by repetition of ferromagnet/metal bilayers. The result
is a consequence of the interconversion of magnon and electron spin currents at
the multiple interfaces. This work opens the possibility to design thin film
heterostructures that may boost the application of thermal spin currents in
spintronics.
