Spin Pumping by Parametrically Excited Exchange Magnons

We experimentally show that exchange magnons can be detected by using a combination of spin pumping and the inverse spin-Hall effect proving its wavelength integrating capability down to the submicrometer scale. The magnons were injected in a ferrite yttrium iron garnet film by parametric pumping and the inverse spin-Hall effect voltage was detected in an attached Pt layer. The role of the density, wavelength, and spatial localization of the magnons for the spin pumping efficiency is revealed.

Figure 1

(a) Sketch of the experimental setup. (b) The magnon spectrum and the mechanism of the parametric pumping process: One quantum of the pump field of ${\omega }_p$ frequency splits into two magnons of ${\omega }_p/2$ frequency.

Figure 2

(a)–(c) Waveforms of the $V_{\mathrm{ISHE}}$ voltage (left column) and pumping schemes for different magnetizing fields $H$. (d) Spin pumping induced voltage dependencies $V_{\mathrm{PM}}(H)$ for parametrically injected magnons (black filled squares) and force excited magnons (gray empty squares). The inset shows the time profile of the pure $V_{\mathrm{PM}}$ signal without spin-Seebeck effect contribution $V_{\mathrm{SB}}$ at $H=1800\mathrm{Oe}$.

Figure 3

(a) Calculated wavelength of the parametrically injected magnons. (b) Normalized dependencies $V_{\mathrm{PM}}(H)$ for different pump powers. The corresponding BLS spectra for two magnetic fields are shown in (c) and (d). The inset in (b) shows the ISHE signal of the parametrically excited magnons at 600 Oe for different pumping powers in comparison to the calculated power dependence.