Composition controlled spin polarization in Co1-xFe xS2 alloys

C. Leighton, M. Manno, A. Cady, J. W. Freeland, L. Wang, K. Umemoto, R. M. Wentzcovitch, T. Y. Chen, C. L. Chien, P. L. Kuhns, M. J R Hoch, A. P. Reyes, W. G. Moulton, E. D. Dahlberg, J. Checkelsky, J. Eckert

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Abstract

The transition metal (TM) chalcogenides of the form TMX2 (X ≤ S or Se) have been studied for decades due to their interesting electronic and magnetic properties such as metamagnetism and metal-insulator transitions. In particular, the Co1-xFexS2 alloys were the subject of investigation in the 1970s due to general interest in itinerant ferromagnetism. In recent years (2000-present) it has been shown, both by electronic structure calculations and detailed experimental investigations, that Co1-xFexS2 is a model system for the investigation of highly spin polarized ferromagnetism. The radically different electronic properties of the two endpoint compounds (CoS2 is a narrow bandwidth ferromagnetic metal, while FeS2 is a diamagnetic semiconductor), in a system forming a substitutional solid solution allows for composition control of the Fermi level relative to the spin split bands, and therefore composition-controlled conduction electron spin polarization. In essence, the recent work has shown that the concept of 'band engineering' can be applied to half-metallic ferromagnets and that high spin polarization can be deliberately engineered. Experiments reveal tunability in both sign and magnitude of the spin polarization at the Fermi level, with maximum values obtained to date of 85% at low temperatures. In this paper we review the properties of Co1-xFexS2 alloys, with an emphasis on properties of relevance to half-metallicity. Crystal structure, electronic structure, synthesis, magnetic properties, transport properties, direct probes of the spin polarization, and measurements of the total density of states at the Fermi level are all discussed. We conclude with a discussion of the factors that influence, or even limit, the spin polarization, along with a discussion of opportunities and problems for future investigation, particularly with regard to fundamental studies of spintronic devices.

Original languageEnglish (US)
Article number315219
JournalJournal of Physics Condensed Matter
Volume19
Issue number31
DOIs
StatePublished - Aug 8 2007

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Spin polarization
Fermi level
polarization
Chemical analysis
Ferromagnetism
Electronic properties
Electronic structure
Magnetic properties
Metamagnetism
ferromagnetism
Electron transport properties
Chalcogenides
Magnetoelectronics
Metal insulator transition
Ferromagnetic materials
electronic structure
magnetic properties
chalcogenides
Transition metals
Solid solutions

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Composition controlled spin polarization in Co1-xFe xS2 alloys. / Leighton, C.; Manno, M.; Cady, A.; Freeland, J. W.; Wang, L.; Umemoto, K.; Wentzcovitch, R. M.; Chen, T. Y.; Chien, C. L.; Kuhns, P. L.; Hoch, M. J R; Reyes, A. P.; Moulton, W. G.; Dahlberg, E. D.; Checkelsky, J.; Eckert, J.

In: Journal of Physics Condensed Matter, Vol. 19, No. 31, 315219, 08.08.2007.

Research output: Contribution to journalArticle

Leighton, C, Manno, M, Cady, A, Freeland, JW, Wang, L, Umemoto, K, Wentzcovitch, RM, Chen, TY, Chien, CL, Kuhns, PL, Hoch, MJR, Reyes, AP, Moulton, WG, Dahlberg, ED, Checkelsky, J & Eckert, J 2007, 'Composition controlled spin polarization in Co1-xFe xS2 alloys', Journal of Physics Condensed Matter, vol. 19, no. 31, 315219. https://doi.org/10.1088/0953-8984/19/31/315219
Leighton, C. ; Manno, M. ; Cady, A. ; Freeland, J. W. ; Wang, L. ; Umemoto, K. ; Wentzcovitch, R. M. ; Chen, T. Y. ; Chien, C. L. ; Kuhns, P. L. ; Hoch, M. J R ; Reyes, A. P. ; Moulton, W. G. ; Dahlberg, E. D. ; Checkelsky, J. ; Eckert, J. / Composition controlled spin polarization in Co1-xFe xS2 alloys. In: Journal of Physics Condensed Matter. 2007 ; Vol. 19, No. 31.
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AU - Cady, A.

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AU - Wang, L.

AU - Umemoto, K.

AU - Wentzcovitch, R. M.

AU - Chen, T. Y.

AU - Chien, C. L.

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