Molecular-Beam Epitaxy (MBE) growth of chemically ordered Co-Pt and Fe-Pt alloy phases

MBE is a powerful synthesis technique for preparation of ordered intermetallic phases since the high rates of surface diffusion allow in-plane chemical ordering to occur at temperatures far below those which are necessary for ordering in bulk samples. This lifting of kinetic constraints enables the phase diagrams to be explored at low temperatures where bulk ordering processes are often too sluggish for phase equilibria to be reached. Specifically, we describe the preparation of epitaxial films (in the thickness range 100 - 1000 angstrom) of ordered intermetallic phases in the Co-Pt and Fe-Pt intermetallic systems. Such phases are of potential importance for magnetic and magneto-optical storage applications. In particular we discuss growth and chemical ordering in epitaxial Co1-xPtx films near x = 0.25, 0.5, and 0.75 as well as Fe1-xPtx films near x = 0.5. Depending on growth conditions these phases order spontaneously during growth with resulting changes in the Kerr spectra. Ordering results in large Kerr rotations (approximately 1 °) in the UV spectral region for the films with x near 0.5.