Direct imaging of the ac component of the pumped spin polarization with element specificity

Abstract

Spin pumping in a ferromagnet/nonferromagnet heterostructure is directly imaged with spatial resolution as well as element selectivity. The time-resolved detection in scanning transmission xray microscopy allows to directly probe the spatial extent of the ac spin polarization in Co-doped ZnO which is generated by spin pumping from an adjacent permalloy microstrip. Comparing the relative phases of the dynamic magnetization component of the two constituents is possible and found to be antiphase. The correlation between the distribution of the magnetic excitation in the permalloy and the Co-doped ZnO reveals that laterally there is no one-to-one correlation. The observed distribution is rather complex, but integrating over larger areas clearly demonstrates that the spin polarization in the nonferromagnet extends laterally beyond the region of the ferromagnetic microstrip. Therefore the observations are better explained by a local spin pumping efficieny and a lateral propagation of the ac spin polarization in the nonferromagnet over the range of a few micrometers.

Magnetization generated by microwave-induced Rashba interaction

“…In case such currents are spin polarized, as happens for electrons injected from magnetic materials, they lead to the creation of magnetic torques that can be exploited to manipulate and control the local magnetization of a ferromagnet 3 . Spin injection of ac and dc currents from ferromagnetic materials were indeed detected and imaged 4 . Yet another tool for efficient manipulation of magnetic order in nano-scale devices depends on the interplay between charge and spin brought about by the spin-orbit interaction 5 which couples the spin and the momentum of the electrons.…”