A strategy for more reliably obtaining Y3Fe5O12 thin films with both low damping and highly spin transparent surface

This paper reports a strategy for more reliably obtaining sputtered thin yttrium–iron–garnet (YIG) films possessing both low magnetic damping (α) and a highly spin transparent surface, which represent two of the most important properties for YIG films applied in spintronic devices. The two key points of this strategy, concluded from our systematical studies, are as follows: oxygen reactive sputtering of a slight Y-rich YIG target to avoid the over-stoichiometry of the Fe component and at the same time minimize oxygen vacancy density; and employing phosphoric acid wet etching to remove the inevitable thin magnetic dead layer formed on the surface. The feasibility of this strategy was proved by the achievement of a high quality 30 nm-thick YIG film. It possesses a ferromagnetic resonance linewidth of only 3.4 Oe at 8 GHz, α of only 4.6 × 10−4, and a very spin-transparent surface, as proved by the measured extremely large spin pumping voltage of 650.1 µV after depositing a 3 nm Pt layer.