Issue 18, 2017

Influence of nanoscale order–disorder transitions on the magnetic properties of Heusler compounds for spintronics

Abstract

Modifications in nanoscale chemical order are used to tune the magnetic properties, namely TC, of Co2FeSixAl1−x (0 < x < 1). High-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) with Z-contrast reveals nanoscale regions of L21 order within a B2 matrix in the off-stoichiometry samples. Perhaps surprisingly, the latter, more chemically disordered structure, exhibits a higher TC. Upon annealing, the off-stoichiometry samples become more homogeneous with the fraction of L21 order decreasing. The short-range order was also investigated using X-ray absorption fine structure (XAFS) measurements at the Co and Fe K edges. Since the local atomic environments of Co atoms in the L21 and B2 structures are identical, the features presented in the Co K edge XAFS data are the same in both cases. By contrast, the L21 and B2 structures exhibit different signatures at the Fe K edge owing to the different chemical environments. Fitting of these spectra confirms the nanoscale chemical disorder observed by HAADF-STEM and the expected role this disorder plays on TC. Our results point to a methodology that might be extended to modify the magnetic and electronic properties of any Heusler compound; chemical disorder can be an engineering tool to realize highly tailored properties.

Graphical abstract: Influence of nanoscale order–disorder transitions on the magnetic properties of Heusler compounds for spintronics

Supplementary files

Article information

Article type
Communication
Submitted
24 Mar 2017
Accepted
20 Apr 2017
First published
02 May 2017
This article is Open Access
Creative Commons BY license

J. Mater. Chem. C, 2017,5, 4388-4392

Influence of nanoscale order–disorder transitions on the magnetic properties of Heusler compounds for spintronics

J. Karel, J. E. Fischer, S. Fabbrici, E. Pippel, P. Werner, M. Vinicius Castergnaro, P. Adler, S. Ouardi, B. Balke, G. H. Fecher, J. Morais, F. Albertini, S. S. P. Parkin and C. Felser, J. Mater. Chem. C, 2017, 5, 4388 DOI: 10.1039/C7TC01241A

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