Bi₂Se₃ interlayer treatments affecting the Y₃Fe₅O₁₂ (YIG) platinum spin Seebeck effect

In this work, we present a method to enhance the longitudinal spin Seebeck effect at platinum/yttrium iron garnet (Pt/YIG) interfaces. The introduction of a partial interlayer of bismuth selenide (Bi₂Se₃, 2.5% surface coverage) interfaces significantly increases (by ∼380%-690%) the spin Seebeck coefficient over equivalent Pt/YIG control devices. Optimal devices are prepared by transferring Bi₂Se₃ nanoribbons, prepared under anaerobic conditions, onto the YIG (111) chips followed by rapid over-coating with Pt. The deposited Pt/Bi₂Se₃ nanoribbon/YIG assembly is characterized by scanning electron microscope. The expected elemental compositions of Bi₂Se₃ and YIG are confirmed by energy dispersive x-ray analysis. A spin Seebeck coefficient of 0.34-0.62 μV/K for Pt/Bi₂Se₃/YIG is attained for our devices, compared to just 0.09 μV/K for Pt/YIG controls at a 12 K thermal gradient and a magnetic field swept from −50 to +50 mT. Superconducting quantum interference device magnetometer studies indicate that the magnetic moment of Pt/Bi₂Se₃/YIG treated chips is increased by ∼4% vs control Pt/YIG chips (i.e., a significant increase vs the ±0.06% chip mass reproducibility). Increased surface magnetization is also detected in magnetic force microscope studies of Pt/Bi₂Se₃/YIG, suggesting that the enhancement of spin injection is associated with the presence of Bi₂Se₃ nanoribbons.