- Lateral confinement effects on the magnetic domains arrangement of MnAs micrometric bars.

FERNANDEZ BALDIS FTORTAROLO M., SIRENA M., STEREN L., VIDAL F., RACHE SALLES B., ETGENS V., EDDRIEF.

Buenos Aires

Conferencia; V At the Frontiers of Condensed Matter; 2010

One of the major challenges of spintronic development nowadays is the capability of integrating semiconductors and ferromagnetic materials in multifunctional devices. In this field, the MnAs alloy is a promising material due to the facts that it presents ferromagnetism until 314K and grows epitaxially on GaAs. The typical size of a magneto-electronic device is 50-1000nm, so it is important to look at the physical properties of MnAs in the nanoscale.  Previous studies performed on MnAs thin films indicate that the structural and magnetic properties of theses materials differ from those of the bulk. A magneto-structural phase coexistence is observed in a broad temperature range just below the Curie temperature, formed by an hexagonal ferromagnetic phase (alpha) and an orthorhombic (beta) paramagnetic phase. This phenomenon is explained in terms of substrate-induced strains. The alpha and the beta phases are organized in a regular pattern of stripes when the film is deposited onto GaAs(100) while they are randomly organized when the film is grown on GaAs(111). In this work we present a study of the magnetic properties of MnAs(120nm)/GaAs(100) micrometric bars. Samples of different width and constant length were fabricated by electron beam lithography. The bars were oriented parallel and perpendicular to the hard-magnetic axis of the system, i.e. c-axis. The magnetic imaging of the micrometric bars was made by magnetic force microscopy between 240C and 110C. Our results indicate that the alpha/beta phase coexistence and the magnetic domain arrangement depend on the size and the orientation of the bars, while the alignment of the stripes parallel to the axis is preserved in both orientation of confinement.