Half-metallic ferromagnetism in hypothetical wurtzite structure chromium chalcogenides
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Ekkes Brück and Frank R. de Boer Van der Waals-Zeeman Instituut, Universiteit van Amsterdam, 1018XE Amsterdam, The Netherlands
Guodong Liu, Haining Hu, Zhuhong Liu, Yuting Cui, and Guangheng Wu State Key Laboratory for Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People’s Republic of China (Received 17 October 2003; accepted 15 June 2004)
The hypothetical wurtzite structure chromium chalcogenides were investigated through first-principle calculation within density-functional theory. All compounds are predicted to be true half-metallic ferromagnets with an integer Bohr magneton of 4 B per unit. Their half-metallic gaps are 1.147, 0.885, and 0.247 eV at their equilibrium volumes for wurtzite-type CrM (M ⳱ S, Se, and Te), respectively. The half-metallicity can be maintained even when volumes are expanded by more than 20% for all compounds and compressed by more than 20%, 20%, and 5%, for CrS, CrSe, and CrTe, respectively.
I. INTRODUCTION
Spintronic devices, which exploit the spin of electrons as well as their charge, have already yielded breakthroughs in information storage and hold the promise of doing the same for random-access memory and microprocessors, as well as a host of other technologies.1–4 One class of materials that has been considered promising for spintronics is the half-metallic ferromagnets (HMFs) that have 100% spin polarized electrons at the Fermi surface.5 After de Groot et al.6 first predicted HMF in Heusler compounds in 1983, several HMFs have been theoretically predicted and experimentally fabricated in the laboratory. In addition to the Heusler alloys, some transition-metal oxides have been found to be HMFs, i.e., Fe3O4,7 CrO2,8,9 perovskites10 and dilute magnetic semiconductors.11,12 Recently, it was found that zinc-blende (ZB) MnAs was a so-called nearly HMF, whereas MnSb, MnBi, CrAs, CrSb, and CrBi in the ZB structure were true HMFs.13–20 Since the hexagonal wurtzite (WZ) structure has the same local structure at the atomic site as the cubic ZB phase, it is reasonable that the promising candi-
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2004.0347 2738
http://journals.cambridge.org
J. Mater. Res., Vol. 19, No. 9, Sep 2004 Downloaded: 13 Mar 2015
dates for HMFs can be found in materials with the WZ-type structure. For the present paper, we systematically investigated the chromium chalcogenides in the WZ-type structure by first-principle calculation within the density-functional theory (DFT). We predict that the WZ-type CrS, CrSe, and CrTe are all true HMFs with the integer magnetic moment of 4.0 B per formula unit, and their theoretical HM gaps are 1.147, 0.885, and 0.247 eV at their equilibrium volumes persist as nonzero with the relatively large volume changing. Since there are some important semiconductors with WZ structure, such as GaN, CdS, and ZnS, these three WZ half-metallic ferromagnets are useful for the spintronic applications if they can be grown epitaxially on these WZ semiconductor substrates
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