Elastic properties of chemically ordered Co3Pt thin films

Abstract

We report room temperature Brillouin light scattering measurements designed to probe the elastic properties of chemically ordered Co3Pt alloy films. A series of 100 nm thick films were deposited by molecular beam epitaxy at different growth temperatures (Tg) between 450 and 950 K. As the deposition temperature increases the lattice structure is observed to transform from a compositionally disordered, mixed fcc/hexagonal phase to a compositionally ordered, purely hexagonal phase, and finally to a compositionally disordered fcc phase. These structural transitions are accompanied by large changes in magnetic anisotropy, new features in the magneto-optical Kerr effect, and changes in the magnetic domain widths which all occur within about a 100 K temperature window centered around Tg=650 K. However, the independent elastic constants show no significant changes in the different films. These findings suggest that macroscopic strain effects are unlikely to underlie the diverse magnetic signatures observed within the chemically ordered phase.

Mechanism of Elastic Softening Behavior in a Superlattice

“…There is a possibility of interdiffusion and formation of the CoPt intermetallic alloy at the interfaces [23]. Bandhu et al [24] measured C ij of Co 3 Pt thin films, and they observed smaller C 33 than that predicted from bulk C 33 of Co and Pt: C Co 3 Pt 33 308 GPa, C Pt111 33 385 GPa, C fcc-Co111 33 367 GPa, and C hcp-Co 33 357 GPa. This result implies that the existence of Co 3 Pt interatomic alloy decreases the macroscopic C 33 of Co=Pt superlattice.…”