Enhanced spin polarization of amorphous F ex S i1-x thin films revealed by Andreev reflection spectroscopy

J. Karel, D. S. Bouma, J. Martinez, Y. N. Zhang, J. A. Gifford, J. Zhang, G. J. Zhao, D. R. Kim, B. C. Li, Z. Y. Huang, R. Q. Wu, Tingyong Chen, F. Hellman

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Abstract

Point contact Andreev reflection spectroscopy has been utilized to determine the spin polarization of both amorphous and crystalline FexSi1-x (0.58<x<0.68) thin films. The amorphous materials exhibited a substantial spin polarization (generally greater than 60%), despite significant changes in magnetization and resistivity. In particular, the polarization value in the x=0.65 amorphous alloy is about 70%, significantly higher than most ferromagnets, including numerous Heusler compounds that are theoretically predicted to be half-metallic ferromagnets. The composition dependence of the spin polarization in the amorphous materials is proportional to (but substantially larger than) the DFT-calculated values. The polarization of a crystalline thin film with x=0.65, by contrast, is only 49%, similar to that of common magnetic metals. The enhanced spin polarization in the amorphous structure is attributed to the modification of the local environments. This work demonstrates that the spin polarization, as well as magnetic moment, anomalous Hall effect, and electrical resistivity, can be tuned by introducing structural disorder as an engineering tool.

Original languageEnglish (US)
Article number064411
JournalPhysical Review Materials
Volume2
Issue number6
DOIs
StatePublished - Jun 27 2018

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ASJC Scopus subject areas

  • Materials Science(all)
  • Physics and Astronomy (miscellaneous)

Cite this

Karel, J., Bouma, D. S., Martinez, J., Zhang, Y. N., Gifford, J. A., Zhang, J., Zhao, G. J., Kim, D. R., Li, B. C., Huang, Z. Y., Wu, R. Q., Chen, T., & Hellman, F. (2018). Enhanced spin polarization of amorphous F ex S i1-x thin films revealed by Andreev reflection spectroscopy. Physical Review Materials, 2(6), [064411]. https://doi.org/10.1103/PhysRevMaterials.2.064411