Metastable tetragonal structure of Fe 100-xGax epitaxial thin films on ZnSe/GaAs(001) substrate

EDDRIEF, M.; ZHENG, Y.; HIDKI, S.; B. RACHE SALLES; J. MILANO; ETGENS, V. H.; MARANGOLO, M.

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

American Physical Society

Año: 2011 vol. 84 p. 161410 - 161410

0163-1829

We investigated by x-ray diffraction the Ga concentration dependences of the structural properties of Fe100−xGax (galfenol) thin films grown on a ZnSe/GaAs(001) substrate, a material known for its high magnetostriction. By molecular beam epitaxy (MBE) we grew a series of (001)-oriented layers without in-plane misorientation, ranging from pure Fe up to x=29.4% Ga. We find a strong Ga-induced tetragonal distortion that conserves the pristine Fe in-plane lattice parameters for all Ga compositions. Supported by theoretical predictions [ R. Wu J. Appl. Phys. 91 7358 (2002)], we attribute this unusual tetragonal distortion to short-range ordering of Ga-Ga pairs along the [001]-growth direction. The low-temperature and out-of-equilibrium MBE growth regime tends to stabilize a strong deformed tetragonal phase (up to c/a∼1.05 for x∼29%). This tetragonal structure is fully released by postgrowth annealing.