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Hexagonal close-packed Ni nanostructures grown on the (001) surface of MgO

2005; American Institute of Physics; Volume: 86; Issue: 13 Linguagem: Inglês

10.1063/1.1890472

1520-8842

Wei Quan Tian, He Sun, Xiaoqing Pan, Jaeeun Yu, M. Yeadon, C. B. Boothroyd, Yuan Ping Feng, R. A. Lukaszew, R. J. Clarke,

Magnetic properties of thin films

We report the in situ microscopy observation of an unnatural phase of Ni, a highly strained hexagonal close-packed (hcp) form which we believe is stabilized by heteroepitaxial growth on the (001) face of MgO. We find that the nanosized hcp nickel islands transform into the normal face-centered cubic structure when the size of the islands exceeds a critical value (about 2.5 nm thick with a lateral size of ∼5nm). The structural transition proceeds via a martensitic change in the stacking sequence of the close-packed planes. The formation of hcp Ni nanostructures with an unusually large crystallographic c∕a ratio (∼6% larger than ideal hcp) is very interesting for spintronic and recording applications where large uniaxial anisotropies are desirable.