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arXiv · 1802.08740

Crystal structure and local ordering in epitaxial Fe$_{100-x}$Ga$_x$/MgO(001) films

Miguel Ciria·Maria Grazia Proietti·Edna C. Corredor·David Coffey·Adrián Begué·César de la Fuente·José I. Arnaudas·Alfonso Ibarra
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Abstract

In this work we present a study of the structural properties of Fe$_{100-x}$ Ga$_x$ grown by Molecular Beam Epitaxy on Mg0(100). We combine long range and local/chemically selective X-ray probes (X-ray Diffraction and X-ray absorption spectroscopy) together with real space imaging by means of Transmission Electron Microscopy and surface sensitive $in situ$ Reflected High Energy Electron Diffraction. For substrate temperature $T_s$ below 400 $^o$C we obtain $bcc$ films while, for $x \approx$ 24 and $T_s \geq$ 400$^o$C the nucleation of the $fcc$ phase is observed. For both systems a Ga anticlustering or local range ordering phenomenon appears. The Ga/Fe composition in the first and second coordination shells of the $bcc$ films is different from that expected for a random Ga distribution and is close to a D0$_3$-like ordered phase, leading to a minimization of the number of Ga-Ga pairs. On the other side, a true long-range D0$_3$ phase is not observed indicating that atomic ordering only occurs at a local scale. Overall, the epitaxial growth procedure presented in this work, first, avoids the formation of a long range ordered D0$_3$ phase, which is known to be detrimental magnetostrictive properties, and second, demonstrates the possibility of growing $fcc$ films at temperatures much smaller than those required to obtain bulk $fcc$ samples.

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Miguel Ciria, Maria Grazia Proietti, Edna C. Corredor, David Coffey, Adrián Begué, César de la Fuente, José I. Arnaudas, Alfonso Ibarra. 2018-02-23. Crystal structure and local ordering in epitaxial Fe$_{100-x}$Ga$_x$/MgO(001) films. https://doi.org/10.1016/j.jallcom.2018.07.120

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