Half-metallicity in highly L21-ordered CoFeCrAl thin films

Y. Jin, P. Kharel, S. R. Valloppilly, X. Z. Li, D. R. Kim, G. J. Zhao, T. Y. Chen, R. Choudhary, A. Kashyap, R. Skomski, D. J. Sellmyer

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Abstract

The structural, magnetic, and electron-transport properties of Heusler-ordered CoFeCrAl thin films are investigated experimentally and theoretically. The films, sputtered onto MgO and having thicknesses of about 100 nm, exhibit virtually perfect single-crystalline epitaxy and a high degree of L21 chemical order. X-ray diffraction and transmission-electron microscopy show that the structure of the films is essentially of the L21 Heusler type. The films are ferrimagnetic, with a Curie temperature of about 390 K, and a net moment of 2 μB per formula unit. The room temperature resistivity is 175 μΩ cm; the carrier concentration and mobility determined from the low temperature (5 K) measurement are 1.2 × 1018 cm-3 and 33 cm2/V s, respectively. In contrast to the well-investigated Heusler alloys such as Co2(Cr1-xFex)Al, the CoFeCrAl system exhibits two main types of weak residual A2 disorder, namely, Co-Cr disorder and Fe-Cr disorder, the latter conserving half-metallicity. Point-contact Andreev reflection yields a lower bound for the spin polarization, 68% at 1.85 K, but our structural and magnetization analyses suggest that the spin polarization at the Fermi level is probably higher than 90%. The high resistivity, spin polarization, and Curie temperature are encouraging in the context of spin electronics.

Original languageEnglish (US)
Article number142410
JournalApplied Physics Letters
Volume109
Issue number14
DOIs
StatePublished - Oct 3 2016

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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    Jin, Y., Kharel, P., Valloppilly, S. R., Li, X. Z., Kim, D. R., Zhao, G. J., Chen, T. Y., Choudhary, R., Kashyap, A., Skomski, R., & Sellmyer, D. J. (2016). Half-metallicity in highly L21-ordered CoFeCrAl thin films. Applied Physics Letters, 109(14), [142410]. https://doi.org/10.1063/1.4964464