Stabilization of bcc Co via epitaxial growth on GaAs.

A new metastable phase of cobalt---body-centered cubic---has been synthesized by use of molecular-beam epitaxial growth to stabilize the crystal structure. Large (1\ifmmode\times\else\texttimes\fi{}1 ${\mathrm{cm}}^{2}$) films have been grown on (110) GaAs and characterized by high-energy electron diffraction, Auger analysis, x-ray diffraction, magnetometry, spin-polarized photoemission, and ferromagnetic resonance. The results indicate a ferromagnetic material very similar to $\ensuremath{\alpha}$-Fe both electronically and magnetically, with a metastable lattice constant ${a}_{0}=2.827$ \AA{}. This technique provides a general approach for the realizing of metastable phases.