The Structure And Magnetic Properties Of Ultrathin Films Of Co-based Alloys

In the recent decades, spintronics and spintronic devices which combine electron charge and spin attract scientists'interest greatly for their potential industrial applications. Thin film magnetism is one of the important research areas. With the decreasing dimensionality, especially to the nanometer scale, brand new phenomena emerges. In the mean time, new technologies for sample preparation and new equipments for magnetic measurement with high sensitivity make it possible to investigate and manipulate the magnetic properties of ultrathin films.Some of my works are listed as follows:1 The magnetocrystalline anisotropy of body-centered-cubic(bcc) Co, which does not exist in nature, is investigated. The crystalline structure and magnetic properties of Co/GaAs(001) are also exploited. With the increasing Co thickness, there is a structural phase transition:from body centered cubic (bcc) to hexagonal close packed (hcp) structure. The critical thickness depends on the growth temperature of Co. The magnetocrystalline anisotropy constants of bcc Co is quantitatively determined by excluding the magnetic effects from hep Co, which consists with all the previous experiments results.2 The correlation between magnetic properties and crystalline structure of bcc FexCo1-x flims and the origin of uniaxial anisotropy are studied. Bcc cubic symmetry does not necessarily require the easy axes of magnetocrystalline anisotropy parallel to <100> directions, which switch from bcc FexCo1-x<100> to<110> directions from Fe rich end to Co rich end. The misfit between GaAs substrate and FexCo1-x films, which could be tuned by Fe composition, manipulates the orientation of easy axis of uniaxial anisotropy.3 The magnetic properties of face-centered-cubic (fcc) CoxPd1-x films and the origin of perpendicular magnetic anisotropy are studied. The easy axes of magnetocrystalline anisotropy are found to switch from<110> to<100> directions, which is different from those of bulk alloys. The transition point is at 50% Co. The possession of perpendicular magnetic anisotropy in films depends on the buffer layer(Au or Cu).4 Submonolayer Mn/Fe/Cu(001) was investigated on the interaction between Mn and Fe. The magnetization and Curie temperature of the whole system are lowered. Mn is found to be antiferromagnetically coupled to Fe and the interaction between Mn...