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Direct Imaging of the ac Component of Pumped Spin Polarization with Element Specificity

S. Pile1, M. Buchner1, V. Ney1, T. Schaffers1,†, J. Lumetzberger1, K. Lenz2, R. Narkowicz2, J. Lindner2, H. Ohldag3,4,‡ et al.

A. Ney1,*

  • 1Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenberger Strasse 69, Linz 4040, Austria
  • 2Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstrasse 400, Dresden 01328, Germany
  • 3Stanford Synchrotron Radiation Laboratory, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
  • 4Department of Physics, University of California Santa Cruz, Santa Cruz, California 95064, USA

  • *andreas.ney@jku.at
  • †Present address: NanoSpin, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland.
  • ‡Present addresses: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA and Department of Material Sciences and Engineering, Stanford University, Stanford, CA 94305, USA.
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Phys. Rev. Applied 14, 034005 – Published 1 September, 2020

DOI: https://doi.org/10.1103/PhysRevApplied.14.034005

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 x-ray microscopy allows us 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 close to 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 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 efficiency and a lateral propagation of the ac spin polarization in the nonferromagnet over the range of a few micrometers.

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Phys. Rev. Applied 14, 034005– Published 1 September, 2020
  • Received 11 May 2020
  • Revised 29 June 2020
  • Accepted 13 July 2020
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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