Letter | Published:

Reading and writing single-atom magnets

Nature volume 543, pages 226228 (09 March 2017) | Download Citation

Abstract

The single-atom bit represents the ultimate limit of the classical approach to high-density magnetic storage media. So far, the smallest individually addressable bistable magnetic bits have consisted of 3–12 atoms1,2,3. Long magnetic relaxation times have been demonstrated for single lanthanide atoms in molecular magnets4,5,6,7,8,9,10,11,12, for lanthanides diluted in bulk crystals13, and recently for ensembles of holmium (Ho) atoms supported on magnesium oxide (MgO)14. These experiments suggest a path towards data storage at the atomic limit, but the way in which individual magnetic centres are accessed remains unclear. Here we demonstrate the reading and writing of the magnetism of individual Ho atoms on MgO, and show that they independently retain their magnetic information over many hours. We read the Ho states using tunnel magnetoresistance15,16 and write the states with current pulses using a scanning tunnelling microscope. The magnetic origin of the long-lived states is confirmed by single-atom electron spin resonance17 on a nearby iron sensor atom, which also shows that Ho has a large out-of-plane moment of 10.1 ± 0.1 Bohr magnetons on this surface. To demonstrate independent reading and writing, we built an atomic-scale structure with two Ho bits, to which we write the four possible states and which we read out both magnetoresistively and remotely by electron spin resonance. The high magnetic stability combined with electrical reading and writing shows that single-atom magnetic memory is indeed possible.

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Acknowledgements

We thank B. Melior for technical assistance and F. Donati for discussions. We acknowledge financial support from the Office of Naval Research. F.D.N. appreciates support from the Swiss National Science Foundation under project numbers P300P2_158468 and PZ00P2_167965, and help from A. Natterer. K.Y. acknowledges support from National Natural Science Foundation of China (grant number 61471337). W.P. thanks the Natural Sciences and Engineering Research Council of Canada for fellowship support. P.W. acknowledges financial support from the German academic exchange service. T.G. thanks B. Delley for discussions and IBM Research for its hospitality.

Author information

Affiliations

  1. IBM Almaden Research Center, San Jose, California 95120, USA

    • Fabian D. Natterer
    • , Kai Yang
    • , William Paul
    • , Philip Willke
    • , Taeyoung Choi
    • , Thomas Greber
    •  & Christopher P. Lutz
  2. Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland

    • Fabian D. Natterer
  3. School of Physical Sciences and Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing 100049, China

    • Kai Yang
  4. IV. Physical Institute, University of Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany

    • Philip Willke
  5. Physik-Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland

    • Thomas Greber
  6. Institute of Basic Science, Center for Quantum Nanoscience, Seoul, South Korea

    • Andreas J. Heinrich
  7. Physics Department, Ewha Womans University, Seoul, South Korea

    • Andreas J. Heinrich

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Contributions

F.D.N. conceived the experiment and wrote the manuscript. F.D.N., K.Y., W.P. and P.W. analysed the data. W.P. conceived the atom-switching routine. C.P.L. and A.J.H. enabled and supervised the project. All authors carried out measurements, discussed the results and contributed to the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Fabian D. Natterer or Andreas J. Heinrich or Christopher P. Lutz.

Reviewer Information Nature thanks N. Lorente, R. Sessoli and W. Wernsdorfer for their contribution to the peer review of this work.

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https://doi.org/10.1038/nature21371

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