Unusual stability of fcc Co(110)/Cu(110)

It is found that thick (1000) films of fcc Co can be stabilized via epitaxial growth onto Cu(110) substrates at room temperature. These metastable films transform into polycrystalline films of the stable hcp phase if annealed to temperatures above 200°C. The unusual stability of the fcc phase in the (110) growth direction is linked with the fact that the phase transformation to hcp involves a major disruption of the crystal structure, compared with, e.g., growth of fcc Co on Cu(111). The stabilization of single-crystal fcc Co at room temperature has enabled measurements of the room temperature magnetic properties in these films, for comparison with hcp Co. © 1993 The American Physical Society.