Solution-Processed Ferrimagnetic Insulator Thin Film for the Microelectronic Spin Seebeck Energy Conversion

Abstract

The longitudinal spin Seebeck effects with a ferro- or ferrimagnetic insulator provide a new architecture of a thermoelectric device that could significantly improve the energy conversion efficiency. Until now, epitaxial yttrium iron garnet (YIG) films grown on gadolinium gallium garnet (GGG) substrates by a pulsed laser deposition have been most widely used for spin thermoelectric energy conversion studies. In this work, we developed a simple route to obtain a highly uniform solution-processed YIG film and used it for the on-chip microelectronic spin Seebeck characterization. We improved the film roughness down to similar to 0.2 nm because the extraction of thermally induced spin voltage relies on the interfacial quality. The on-chip microelectronic device has a dimension of 200 mu m long and 20 mu m wide. The solution-processed 20 nm thick YIG film with a 10 nm Pt film was used for the spin Seebeck energy converter. For a temperature difference of Delta T approximate to 0.036 K applied on the thin YIG film, the obtained Delta V approximate to 28 mu V, which is equivalent to S-LSSE approximate to 80.4 nV/K, is close to the typical reported values for thick epitaxial YIG films. The temperature and magnetic field-dependent behaviors of spin Seebeck effects in our YIG films suggest active magnon excitations through the noncoherent precession channel. The effective SSE generation with the solution-processed thin YIG film provides versatile applications of the spin thermoelectric energy conversion.