Materials Transactions Online

Materials Transactions, Vol.47 No.01 (2006) pp.15-19
© 2006 The Japan Institute of Metals

Epitaxial Growth of Ordered Co2(Cr1-xFex)Al Full-Heusler Alloy Films on Single Crystal Substrates

Susumu Okamura1,, Aya Miyazaki1,, Nobuki Tezuka1,2, Satoshi Sugimoto1 and Koichiro Inomata1,2

1Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
2CREST-JST, Kawaguchi 332-0012, Japan

We have investigated the structural and magnetic properties for Co2(Cr1-xFex)Al (x=0.4, 0.6 and 1.0) full-Heusler alloy films deposited on MgO(001), MgO(011) and sapphire (a-plane) substrates by magnetron sputtering. Substrate temperatures were varied from ambient temperature to 773 K. The XRD patterns reveal that the Co2(Cr1-xFex)Al films grow epitaxially with the (001), (112), and (011) orientations on MgO(001), MgO(110) and sapphire (a-plane) substrates, respectively. The Co2(Cr1-xFex)Al films deposited at room temperature (RT) crystallize into the A2 structure, whereas the films deposited at 673 K showed the B2 structure. Especially, for the Co2FeAl (x=1) films deposited on an MgO(001) substrate at 773 K, the crystal structure is determined to be the L21 structure with a flat surface. The saturation magnetization of Co2FeAl films with the B2 and L21 structures exhibits almost the 5 μB/f.u., whereas those of Co2(Cr1-xFex)Al (x=0.4, 0.6) show a reduction from the theoretical values. This reduction of the saturation magnetization might be due to the anti-ferromagnetic coupling between Cr--Cr atoms.

(Received 2005/7/11; Accepted 2005/12/1; Published 2006/1/15)

Keywords: half-metal, cobalt--chromium--iron--aluminum, full-Heusler alloy, thin film, L21 structure

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