Thin epitaxial films of the Heusler compound Co2Cr0.6Fe0.4Al

We prepared thin films of the Heusler compound Co2Cr0.6Fe0.4Al with the B2 structure on a-plane (1 1 2¯ 0) Al2O3 by sputtering. Films grown at high temperatures (T⩾600∘C) on Al2O3 are fully epitaxial with the (1 1 0) and (1 1¯ 0) planes of the film parallel to the (1 1 2¯ 0) and (0 0 0 1) planes of the substrate, respectively. These epitaxial films possess a higher surface roughness than films grown at room temperature. The films show nearly rectangular hysteresis loops with coercive fields of the order of 10 mT. Magnetooptical Kerr measurements show an in-plane anisotropy of the magnetization with the easy axis in {001} direction. Hall measurements show a strong anomalous Hall effect and a weak normal Hall voltage signalling the existence of a compensated Fermi surface.