Wideband and On-Chip Excitation for Dynamical Spin Injection into Graphene

Left: schematics of the spin injection by ferromagnetic resonance, where the brown part corresponds to a ferromagnetic permalloy pad that is driven into resonance with an externally applied RF field (hRF), the grey part corresponds to the graphene layere and the blue part to a Pt strip that is used a spin detector. Right: This graph shows the voltage that builds up at the detector as a function of RF frequency. At resonance, a clear spin signal is detected.

Graphene is an ideal material for spin transport, as very long spin-relaxation times and lengths can
be achieved even at room temperature. However, electrical spin injection is challenging due to the
conductivity-mismatch problem. Spin pumping driven by ferromagnetic resonance (FMR) is a neat way to circumvent this problem, as it produces a pure spin current in the absence of a charge current. Here, we demonstrate spin pumping into single-layer graphene using a micron-sized permalloy (Ni80Fe20) pad, which we drive into FMR. The graphene layer, attached to the permalloy pad, adds a channel for the loss of spin polarization in the permalloy pad. As a consequence, both an AC and DC spin current is emitted into the graphene layer. We detect the DC component of this spin current with the aid of a the inverse spin Hall voltage that builds up at a Pt electrode placed a micrometer away.

David Indolese, Simon Zihlmann, Péter Makk, Christian Jünger, Kishan Thodkar, and Christian
Paper: Spin-pumping into graphene by FMR

Paper on spin injection into graphene by spin pumping using FMR