For the evaluation of enhancement in α, ferromagnetic resonance (FMR) measurements are carried out using a vector network analyzer.
#SPIN PUMPING APL HOF FMAN GENERATOR#
For spin pumping induced ISHE measurements, a microwave signal of a fixed frequency is applied to the ACPS waveguide using a signal generator (SG) and a dc voltage is measured across the NM/Cu/Py trilayers as a function of H b. A bias field H b is applied along the z-direction shown in Fig. In the ACPS strip, the width of signal line is 60 μm, the width of ground line is 180 μm, and the signal-ground spacing is 30 μm. Then, in the last step, Ta (5 nm)/Cu (150 nm) asymmetric coplanar strips (ACPS) and dc probe pads are patterned and sputter deposited simultaneously. In the next step, a 640 μm × 630 μm × 30 nm SiO 2 layer is deposited to insulate the Py layer. In all devices, the thickness of NM (Ta or Pt) layer is 10 nm and the thickness of NiFe (Py) layer is 20 nm. First, 800 μm × 600 μm NM/Cu/Ni 81Fe 19 trilayers are fabricated by sputter deposition with the Cu thickness ranging from 0 to 10 nm for different devices. The devices were fabricated using photolithography and lift-off process. The cross section of the device is shown in Fig. In addition, we report the spin diffusion length in Ta to be 8 nm and spin Hall angle to be 0.021–0.033.įigure 1(a) shows a schematic of the device with the measurement set up. We find that the effective g ↑ ↓ increases in the presence of Cu interlayer in Ta/Cu/Py devices but decreases in Pt/Cu/Py devices. Experiments have been conducted to measure ISHE induced by spin pumping in NM, as well as the enhancement of α in NM/Cu/Py devices (NM = Ta, Pt). The aim of this study is to observe the effect of changing the NM/FM interface on g ↑ ↓ by insertion of a Cu interlayer. 17 Previous reports have shown that the spin pumping efficiency can be suppressed by the presence of a thin layer of MgO, 18 nano oxide, 19 or titanium 20 at the NM/FM interface. 16 The properties of the NM/FM interface, quantified by spin mixing conductance ( g ↑ ↓), are also an important determinant of the spin pumping efficiency. 14,15 The contribution of surface spin waves to spin pumping signal has been discussed, and it has been shown that spin waves dramatically enhance the spin pumping induced ISHE signals. 9–11 The spin pumping efficiency can be enhanced by optimizing the magnetization angle out-of-plane of the film, 12 by spin wave mode selection, 13 by chemical modification of FM surface by in situ etching, or by using H 2SO 4/H 2O 2 mixture for cleaning FM surface.
In recent years, the spin pumping induced spin current has been most commonly measured as an electric signal via the inverse spin Hall effect (ISHE) in NM 5–8 or as an enhancement in the Gilbert damping ( α) of the FM.
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