title: Spin pumping in magnetic trilayer structures with an MgO barrier.
abstract: We present a study of the interaction mechanisms in magnetic trilayer structures with an MgO barrier grown by molecular beam epitaxy. The interlayer exchange coupling, Aex, is determined using SQUID magnetometry and ferromagnetic resonance (FMR), displaying an unexpected oscillatory behaviour as the thickness, tMgO, is increased from 1 to 4 nm. Transmission electron microscopy confirms the continuity and quality of the tunnelling barrier, eliminating the prospect of exchange arising from direct contact between the two ferromagnetic layers. The Gilbert damping is found to be almost independent of the MgO thickness, suggesting the suppression of spin pumping. The element-specific technique of x-ray detected FMR reveals a small dynamic exchange interaction, acting in concert with the static interaction to induce coupled precession across the multilayer stack. These results highlight the potential of spin pumping and spin transfer torque for device applications in magnetic tunnel junctions relying on commonly used MgO barriers.
authors.affiliation: Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, United Kingdom.|Magnetic Spectroscopy Group, Diamond Light Source, Didcot, OX11 0DE, United Kingdom.
authors.forename: A A
authors.initials: AA
authors.lastname: Baker
authors.affiliation: Magnetic Spectroscopy Group, Diamond Light Source, Didcot, OX11 0DE, United Kingdom.
authors.forename: A I
authors.initials: AI
authors.lastname: Figueroa
authors.affiliation: Department of Physics, University of York, Heslington, York, YO10 5DD, United Kingdom.
authors.forename: D
authors.initials: D
authors.lastname: Pingstone
authors.affiliation: Department of Physics, University of York, Heslington, York, YO10 5DD, United Kingdom.
authors.forename: V K
authors.initials: VK
authors.lastname: Lazarov
authors.affiliation: Magnetic Spectroscopy Group, Diamond Light Source, Didcot, OX11 0DE, United Kingdom.
authors.forename: G
authors.initials: G
authors.lastname: van der Laan
authors.affiliation: Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, United Kingdom.
authors.forename: T
authors.initials: T
authors.lastname: Hesjedal