Atomic Scale Control of Spin Current Transmission at Interfaces

Ferromagnet/heavy metal bilayers represent a central building block for spintronicdevices where the magnetization of the ferromagnet can be controlled by spin currents generatedin the heavy metal. The efficiency of spin current generation is paramount. Equally important isthe efficient transfer of this spin current across the ferromagnet/heavy metal interface. Here, weshow theoretically and experimentally that for Ta as heavy metal the interface only partiallytransmits the spin current while this effect is absent when Pt is used as heavy metal. This is due tomagnetic moment reduction at the interface caused by 3d-5d hybridization effects. We showthat this effect can be avoided by atomically thin interlayers. On the basis of our theoreticalmodel we conclude that this is a general effect and occurs for all 5d metals with less than half-filled 5d shell