Spin dynamics in the spacer of an interlayer-coupledFe/Fe0.57Si0.43/Fetrilayer probed with nuclear resonant scattering of synchrotron radiation

Abstract

Using nuclear resonant scattering of synchrotron radiation, we investigated the origin of the interlayer coupling in $\text{Fe}/{\text{Fe}}_{0.57}{\text{Si}}_{0.43}/\text{Fe}$ multilayers. The sensitivity of the technique to dynamical processes on a nanosecond timescale and the choice of different isotopes during the growth of the heterostructure allowed us to selectively probe the temperature dependence of the spin dynamics in the spacer layer. Combining these results with macroscopic magnetization measurements, it is shown that the static magnetic ordering in the ${\text{Fe}}_{0.57}{\text{Si}}_{0.43}$ spacer layer leads to the suppression of the interlayer coupling at low temperatures. Above 150 K, fluctuating magnetic Fe moments in the ${\text{Fe}}_{0.57}{\text{Si}}_{0.43}$ spacer with characteristic frequencies in the MHz regime give rise to a biquadratic interlayer coupling between the iron layers.