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

Abstract

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.

Authors:
 [1];  [2];  [3];  [4];  [3];  [3];  [3];  [3];  [3];  [3];  [5];  [3];  [2]
  1. Monash Univ., Melbourne, VIC (Australia). Dept. of Materials Science and Engineering; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Physics
  3. Arizona State Univ., Tempe, AZ (United States). Dept. of Physics
  4. Univ. of Electronic Science and Technology of China, Chengdu (China). School of Energy Science and Engineering
  5. Univ. of California, Irvine, CA (United States). Dept. of Physics and Astronomy
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Spins and Heat in Nanoscale Electronic Systems (SHINES); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Irvine, CA (United States); Arizona State Univ., Tempe, AZ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1479419
Alternate Identifier(s):
OSTI ID: 1457499
Grant/Contract Number:  
AC02-05CH11231; SC0012670; FG02-05ER46237
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review Materials
Additional Journal Information:
Journal Volume: 2; Journal Issue: 6; Journal ID: ISSN 2475-9953
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ferromagnetism; spin injection; spin polarization; spintronics

Citation Formats

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., and Hellman, F. Enhanced spin polarization of amorphous FexSi1-x thin films revealed by Andreev reflection spectroscopy. United States: N. p., 2018. Web. doi:10.1103/PhysRevMaterials.2.064411.
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. Enhanced spin polarization of amorphous FexSi1-x thin films revealed by Andreev reflection spectroscopy. United States. doi:10.1103/PhysRevMaterials.2.064411.
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., and Hellman, F. Wed . "Enhanced spin polarization of amorphous FexSi1-x thin films revealed by Andreev reflection spectroscopy". United States. doi:10.1103/PhysRevMaterials.2.064411. https://www.osti.gov/servlets/purl/1479419.
@article{osti_1479419,
title = {Enhanced spin polarization of amorphous FexSi1-x thin films revealed by Andreev reflection spectroscopy},
author = {Karel, J. and Bouma, D. S. and Martinez, J. and Zhang, Y. N. and Gifford, J. A. and Zhang, J. and Zhao, G. J. and Kim, D. R. and Li, B. C. and Huang, Z. Y. and Wu, R. Q. and Chen, T. Y. and Hellman, F.},
abstractNote = {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.},
doi = {10.1103/PhysRevMaterials.2.064411},
journal = {Physical Review Materials},
number = 6,
volume = 2,
place = {United States},
year = {2018},
month = {6}
}