We have investigated the structural and magnetic properties for Co 2(Cr 1-xFe x)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 Co 2(Cr 1-xFe x)Al films grow epitaxially with the (001), (112), and (011) orientations on MgO(001), MgO(110) and sapphire (a-plane) substrates, respectively. The Co 2(Cr 1-xFe x)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 Co 2FeAl (x = 1) films deposited on an MgO(001) substrate at 773 K, the crystal structure is determined to be the L2 1 structure with a flat surface. The saturation magnetization of Co 2FeAl films with the B2 and L2 1 structures exhibits almost the 5 μ B/f-u., whereas those of Co 2(Cr 1-xFe x)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.
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