Enhanced spin polarization of amorphous FexSi1-x thin films revealed by Andreev reflection spectroscopy

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. Y.; Hellman, F.

doi:10.1103/PhysRevMaterials.2.064411

Title: Enhanced spin polarization of amorphous $F e_{x} S i_{1 - x}$ thin films revealed by Andreev reflection spectroscopy

Journal Article · Wed Jun 27 00:00:00 EDT 2018 · Physical Review Materials

DOI:https://doi.org/10.1103/PhysRevMaterials.2.064411· OSTI ID:1479419

Karel, J. ^[1]; Bouma, D. S. ^[2]; Martinez, J. ^[3]; Zhang, Y. N. ^[4]; Gifford, J. A. ^[3]; Zhang, J. ^[3]; Zhao, G. J. ^[3]; Kim, D. R. ^[3]; Li, B. C. ^[3]; Huang, Z. Y. ^[3]; Wu, R. Q. ^[5]; Chen, T. Y. ^[3]; Hellman, F. ^[2]

Monash Univ., Melbourne, VIC (Australia). Dept. of Materials Science and Engineering; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Physics
Arizona State Univ., Tempe, AZ (United States). Dept. of Physics
Univ. of Electronic Science and Technology of China, Chengdu (China). School of Energy Science and Engineering
Univ. of California, Irvine, CA (United States). Dept. of Physics and Astronomy

Point contact Andreev reflection spectroscopy has been utilized to determine the spin polarization of both amorphous and crystalline $$\mathrm{F}{\mathrm{e}}_{x}\mathrm{S}{\mathrm{i}}_{1{-}x}$$ ($0.58<x<0.68$) 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. Finally, 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.

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Research Organization:: Energy Frontier Research Centers (EFRC) (United States). Spins and Heat in Nanoscale Electronic Systems (SHINES); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES)

Grant/Contract Number:: AC02-05CH11231; SC0012670; FG02-05ER46237

OSTI ID:: 1479419

Alternate ID(s):: OSTI ID: 1457499

Journal Information:: Physical Review Materials, Vol. 2, Issue 6; ISSN 2475-9953

Publisher:: American Physical Society (APS)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 7 works

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Itinerant ferromagnetism and intrinsic anomalous Hall effect in amorphous iron-germanium Bouma, D. S.; Chen, Z.; Zhang, B. arXiv https://doi.org/10.48550/arxiv.1908.06055	text	January 2019

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Title: Enhanced spin polarization of amorphous F e x S i 1 - x thin films revealed by Andreev reflection spectroscopy

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