Interfacial chemical states and recoverable spin pumping in YIG/Pt

Ion etching is an essential step in the processing of spintronic devices. In this work, we investigated the role of argon ion (Ar+) bombardment in the spin pumping and inverse spin Hall effect in the Y3Fe5O12/Pt (YIG/Pt) heterostructure. The inverse spin Hall voltage is found to reduce by an order of two when the argon ion bombardment is employed on the YIG surface before the deposition of the Pt layer. This giant inhibition of spin injection efficiency is undesirable. In this work, we propose an experimental technique for its recovery via a chemical route. The interface property and chemical state were identified by transmission electron microscopy, Raman spectroscopy, and x-ray photoelectron spectroscopy. We found that the argon ion bombardment on the YIG surface leads to an increase in the ratio of Fe2+ ions in the YIG/Pt interface region. Moreover, the interface magnetic moment reduces in the presence of Fe2+ ions, which resulted in the decrease in spin injection efficiency. A strong oxidizing solution (a mixture of concentrated H2SO4 and 30% H2O2 of 1:1 volume ratio) was used to recover the valence of iron and subsequently the interface magnetic moment. Our results are helpful for the understanding of the importance of interface properties and the optimization of spintronic device processing technology.