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Chen J, Bovensiepen U, Eschenlohr A, Müller T, Elliott P, Gross EKU, Dewhurst JK, Sharma S. Competing Spin Transfer and Dissipation at Co/Cu(001) Interfaces on Femtosecond Timescales. PHYSICAL REVIEW LETTERS 2019; 122:067202. [PMID: 30822073 DOI: 10.1103/physrevlett.122.067202] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 11/28/2018] [Indexed: 05/23/2023]
Abstract
By combining interface-sensitive nonlinear magneto-optical experiments with femtosecond time resolution and ab initio time-dependent density functional theory, we show that optically excited spin dynamics at Co/Cu(001) interfaces proceeds via spin-dependent charge transfer and back transfer between Co and Cu. This ultrafast spin transfer competes with dissipation of spin angular momentum mediated by spin-orbit coupling already on sub 100 fs timescales. We thereby identify the fundamental microscopic processes during laser-induced spin transfer at a model interface for technologically relevant ferromagnetic heterostructures.
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Affiliation(s)
- J Chen
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, Lotharstraße 1, 47057 Duisburg, Germany
| | - U Bovensiepen
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, Lotharstraße 1, 47057 Duisburg, Germany
| | - A Eschenlohr
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, Lotharstraße 1, 47057 Duisburg, Germany
| | - T Müller
- Theory Department, Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
| | - P Elliott
- Theory Department, Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
| | - E K U Gross
- Theory Department, Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
| | - J K Dewhurst
- Theory Department, Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
| | - S Sharma
- Theory Department, Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany and Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Strasse 2A, 12489 Berlin, Germany
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Kukreja R, Bonetti S, Chen Z, Backes D, Acremann Y, Katine JA, Kent AD, Dürr HA, Ohldag H, Stöhr J. X-ray Detection of Transient Magnetic Moments Induced by a Spin Current in Cu. PHYSICAL REVIEW LETTERS 2015; 115:096601. [PMID: 26371670 DOI: 10.1103/physrevlett.115.096601] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Indexed: 06/05/2023]
Abstract
We have used a MHz lock-in x-ray spectromicroscopy technique to directly detect changes in magnetic moment of Cu due to spin injection from an adjacent Co layer. The elemental and chemical specificity of x rays allows us to distinguish two spin current induced effects. We detect the creation of transient magnetic moments of 3×10^{-5}μ_{B} on Cu atoms within the bulk of the 28 nm thick Cu film due to spin accumulation. The moment value is compared to predictions by Mott's two current model. We also observe that the hybridization induced existing magnetic moments at the Cu interface atoms are transiently increased by about 10% or 4×10^{-3}μ_{B} per atom. This reveals the dominance of spin-torque alignment over Joule heat induced disorder of the interfacial Cu moments during current flow.
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Affiliation(s)
- R Kukreja
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Department of Materials Science and Engineering, Stanford University, 496 Lomita Mall, Stanford, California 94305, USA
| | - S Bonetti
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Department of Physics, Stanford University, 382 Via Pueblo Mall, Stanford, California 94305, USA
| | - Z Chen
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
- Department of Physics, Stanford University, 382 Via Pueblo Mall, Stanford, California 94305, USA
| | - D Backes
- Physics Department, New York University, 4 Washington Place, New York, New York 10003, USA
| | - Y Acremann
- Laboratorium für Festkörperphysik, ETH Zürich, HPF C 5, Otto-Stern-Weg 1, Zürich 8093, Switzerland
| | - J A Katine
- HGST, a Western Digital Company, 3403 Yerba Buena Road, San Jose, California 95135, USA
| | - A D Kent
- Physics Department, New York University, 4 Washington Place, New York, New York 10003, USA
| | - H A Dürr
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - H Ohldag
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - J Stöhr
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
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MacFarlane WA. Implanted-ion βNMR: A new probe for nanoscience. SOLID STATE NUCLEAR MAGNETIC RESONANCE 2015; 68-69:1-12. [PMID: 25863576 DOI: 10.1016/j.ssnmr.2015.02.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 02/09/2015] [Accepted: 02/11/2015] [Indexed: 06/04/2023]
Abstract
NMR detected by radioactive beta decay, β-NMR, is undergoing a renaissance largely due to the availability of high intensity low energy beams of the most common probe ion, Li+8, and dedicated facilities for materials research. The radioactive detection scheme, combined with the low energy ion beam, enable depth resolved NMR measurements in crystals, thin films and multilayers on depth scales of 2-200 nm. After a brief historical introduction, technical aspects of implanted-ion β-NMR are presented, followed by a review of recent applications to a wide range of solids.
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Affiliation(s)
- W A MacFarlane
- Chemistry Department, University of British Columbia, 2036 Main Mall, Vancouver, Canada V6T 1Z1.
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Gao L, Jiang X, Yang SH, Rice PM, Topuria T, Parkin SSP. Increased tunneling magnetoresistance using normally bcc CoFe alloy electrodes made amorphous without glass forming additives. PHYSICAL REVIEW LETTERS 2009; 102:247205. [PMID: 19659044 DOI: 10.1103/physrevlett.102.247205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Indexed: 05/28/2023]
Abstract
Using cross-section transmission electron microscopy we show that films of CoFe alloys, sandwiched between two conventional amorphous materials, are amorphous when less than approximately 25-30 A thick. When these amorphous layers are integrated into magnetic tunnel junctions with amorphous alumina tunnel barriers, significantly higher tunneling magnetoresistance is found compared to when these layers are made crystalline (e.g., by heating or by thickening them). We postulate that this is likely due to changes in interfacial bonding at the alumina-CoFe interface. Indeed, x-ray emission spectroscopy shows a significant increase in the Fe, but not the Co, 3d density of states at the Fermi energy for thin amorphous CoFe layers.
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Affiliation(s)
- Li Gao
- IBM Research Division, Almaden Research Center, San Jose, California 95120, USA
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