  We derive the Onsager response matrix of fluctuation-mediated spin-collinear
transport through a ferromagnetic insulator and normal metal interface driven
by a temperature difference, spin accumulation, or magnetic field. We predict
magnon-squeezing spin currents, magnetic field-induced cooling (magnon Peltier
effect), temperature induced magnetization (thermal magnetic field) as well as
universal spin Seebeck/Peltier coefficients.
