We have used oxygen-plasma-assisted molecular-beam epitaxy (OPA-MBE) to grow CoxTi1−xO2 anatase on SrTiO3(001) for x=∼0.01–0.10, and have measured the structural, compositional, and magnetic properties of the resulting films. Whether epitaxial or polycrystalline, these CoxTi1−xO2 films are ferromagnetic semiconductors at and above room temperature. However, the magnetic and structural properties depend critically on the Co distribution, which varies widely with growth conditions. Co is substitutional in the anatase lattice and in the +2 formal oxidation state in ferromagnetic CoxTi1−xO2. The magnetic properties of OPA-MBE grown material are significantly better than those of analogous pulsed laser deposition-grown material.

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Growth of epitaxial films of the L1 0 phase of FePt, with the tetragonal c axis along either the film normal or in-plane, is described. Films were grown by coevaporation of Fe and Pt, under ultrahigh vacuum conditions, onto a seed film of Pt grown on MgO or SrTiO 3 substrates. The perpendicular or in-plane orientation of the c axis was controlled by selecting the ͑001͒ or ͑110͒ substrate plane, respectively. Nearly complete chemical ordering was achieved for growth at 500°C for both orientations. Magnetic and magneto-optical characterization of these films confirmed the huge magnetic anisotropy expected for this phase. In the most highly ordered films, anisotropy fields in excess of 120 kOe were measured.

Ultrashort pulse laser techniques are applied to study optically induced modulation in exchange biased ferromagnetic/antiferromagnetic ( FM /AF) thin bilayer films ( NiFe͞NiO). Photoexcitation of the FM / AF interface with subpicosecond laser pulses induces large modulation in the unidirectional exchange bias field (H ex ) on an ultrashort time scale. The "unpinning" of the exchange bias leads to coherent magnetization rotation in the permalloy film which is time resolved by the experiment and corresponds to a large modulation in the magnetization component (DM Z ͞M S ϳ 0.5), on a time scale of 100 psec.[S0031-9007(99)09042-0]

The structural and magnetic properties of 1000-Å-thick epitaxial FexPt1−x(001) alloy films, grown by molecular beam epitaxy with x≂0.5, have been studied as a function of growth temperature. X-ray diffraction analysis showed that the long-range order parameter increased from near zero for films grown at 100 °C to a maximum of 0.93 in films grown at 500 °C. Over this range the magnetic easy axis changed from in-plane to perpendicular and the polar Kerr rotation increased strongly. Spontaneous long-range ordering in these films has an activation energy ∼0.2 eV, consistent with an energy barrier for surface and step down diffusion.