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# Long-distance spin transport in a disordered magnetic insulator

## Abstract

Spin transport through magnetic insulators via magnons has been explored for a variety of crystalline materials. Here we show dramatic effects of spin transport through an amorphous magnetic insulator, which is both magnetically and structurally disordered. We observe spin flow though amorphous yttrium-iron-garnet (a-YIG) thin films in a non-local geometry by use of the spin Hall and inverse spin Hall effects in platinum strips separated by ten or more micrometres. By comparing a-YIG grown on suspended micromachined thermal isolation platforms to the same film on bulk substrates, we show strong effects of in-plane thermal gradients on spin transport in the disordered film. The resulting signals are orders of magnitude larger than those seen in crystalline magnetic insulators, and easily measurable even for distances greater than 100 μm. In analogy to heat transport in glasses, where a range of vibrational excitations can allow large thermal conductivities, we suggest that efficient spin transport in disordered systems can occur via a similar spectrum of excitations that relies on strong local exchange interactions and does not require long-range order. This opens a new area for experimental and theoretical studies of spin transport, and sets a new direction in materials science for magnonic and spintronic devices.

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## Acknowledgements

We thank A. Hojem for helpful discussions and assistance in the lab, D. Schmidt for assistance with optical imaging, the NIST Boulder magnetics group for access to the SQUID magnetometer and advice, X. Fan and A. Humphries for deposition of the SiO2 film, and J. Nogan and the IL staff at CINT for guidance and training in fabrication techniques. D.W. and B.L.Z. gratefully acknowledge support from the NSF (DMR-1410247). This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the US Department of Energy (DOE) Office of Science by Los Alamos National Laboratory (Contract DE-AC52-06NA25396) and Sandia National Laboratories (Contract DE-AC04-94AL85000). The growth of the YIG films at CSU was supported by the SHINES, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under Award SC0012670.

## Author information

Authors

### Contributions

Thermal isolation platforms were designed by D.W. and B.L.Z., and fabricated, measured, and analysed by D.W. under supervision of B.L.Z. a-YIG films were deposited by T.L. under supervision of M.W. XRD on films and YIG substrates was performed and analysed by D.B. FEM thermal calculations were performed by D.W. with consultation and input from B.L.Z. B.L.Z. initiated the study with consultation from M.W. D.W. and B.L.Z. wrote the manuscript with contributions from all authors.

### Corresponding author

Correspondence to Barry L. Zink.

## Ethics declarations

### Competing interests

The authors declare no competing financial interests.

## Supplementary information

### Supplementary information

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Wesenberg, D., Liu, T., Balzar, D. et al. Long-distance spin transport in a disordered magnetic insulator. Nature Phys 13, 987–993 (2017). https://doi.org/10.1038/nphys4175

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• DOI: https://doi.org/10.1038/nphys4175

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