L. Ilver

Postgrowth annealing of (Ga,Mn) As under As capping: An alternative way to increase TC

In situ postgrowth annealing of (Ga,Mn)As layers under As capping is adequate for achieving high Curie temperatures (TC) in a similar way as ex situ annealing in air or in N2 atmosphere practiced earlier. Thus, the first efforts give an increase of TC from 68 to 145 K after 2 h annealing at 180 °C. These data, in combination with lattice parameter determinations and photoemission results, show that the As capping acts as an efficient sink for diffusing Mn interstitials.

Structural and magnetic properties of GaMnAs layers with high Mn-content grown by migration-enhanced epitaxy on GaAs(100) substrates

Ferromagnetic GaMnAs containing up to 10% Mn has been grown by migration-enhanced epitaxy at a substrate temperature of 150 °C. The lattice constant of hypothetical zinc-blende structure MnAs is determined to be 5.90 A, which deviates somewhat from previously reported values. This deviation is ascribed to growth-condition-dependent density of point defects. Magnetization measurements showed an onset of ferromagnetic ordering around 75 K for the GaMnAs layer with 10% Mn. This means that the trend of falling Curie temperatures with increasing Mn concentrations above 5.3% is broken.

Angular-resolved u.v. photoemission from single crystals of copper

Abstract Angular-resolved u.v.-photoemission energy distributions have been measured from single crystals of Cu. The observed peak energies are in agreement with calculations using direct interband transitions in the bulk. Only one peak falls outside this interpretation and its origin is discussed.

Magnetization reversal in GaMnAs layers studied by Kerr effect

In this letter, magnetization reversal is investigated in (Ga,Mn)As thin films using the magneto-optical Kerr effect. A Stoner–Wohlfart model, modified to take into account the existence of magnetic reversal discontinuities associated with nucleation and propagation phenomena allows us to estimate most of the characteristic constants. These results demonstrate a reversal behavior analogous to that observed in metallic magnetic layers (coherent rotation followed by a nucleation propagation process). The dynamic study at T=20 K shows a strong increase of the coercivity with the increase of dH/dt. This effect is related to the random distribution of Mn magnetic ions in the lattice.

Ferromagnetism and interlayer exchange coupling in short-period (Ga,Mn)As/GaAs superlattices

Magnetic properties of (Ga,Mn)As/GaAs superlattices are investigated. The structures contain magnetic (Ga,Mn)As layers, separated by thin layers of nonmagnetic GaAs spacer. The short-period Ga0.93Mn0.07As/GaAs superlattices exhibit a paramagnetic-to-ferromagnetic phase transition close to 60 K, for thicknesses of (Ga,Mn)As down to 23 A. For Ga0.96Mn0.04As/GaAs superlattices of similar dimensions, the Curie temperature associated with the ferromagnetic transition is found to oscillate with the thickness of nonmagnetic spacer. The observed oscillations are related to an interlayer exchange interaction mediated by the polarized holes of the (Ga,Mn)As layers.

The electronic structure of In- and As-terminated InAs(001) surfaces

Abstract The InAs(001) 2 × 4 and 4 × 2 surfaces have been investigated by angle-resolved photoemission. The X 3 and X 5 points were found to be located 6.0 and 2.7 eV below the valence band maximum, respectively, and the dispersion of bulk bands along the Г-X direction in the bulk Brillouin zone were well described by a theoretical calculation. From angle-resolved valence band spectra measured along the high symmetry directions [110] and [110], three surface induced states were identified on both the InAs(001)4 × 2 and the InAs(001)2 × 4 surface.

Photoemission studies of Ga 1 − x Mn x As : Mn concentration dependent properties

Using angle-resolved photoemission, we have investigated the development of the electronic structure and the Fermi level pinning in

Angular dependences in u.v.-photoemission from single crystals of Au

{\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}

The effect of the first GaN monolayer on the nitridation damage of molecular beam epitaxy grown GaN on GaAs(001)

with Mn concentrations in the range 1%\char21{}6%. We find that the Mn-induced changes in the valence-band spectra depend strongly on the Mn concentration, suggesting that the interaction between the Mn ions is more complex than assumed in earlier studies. The relative position of the Fermi level is also found to be concentration dependent. In particular we find that for concentrations around 3.5%\char21{}5% it is located very close to the valence-band maximum, which is in the range where metallic conductivity has been reported in earlier studies. For concentrations outside this range, larger as well as smaller, the Fermi level is found to be pinned at about 0.15 eV higher energy.

Enhancing the bioactivity of zirconia and zirconia composites by surface modification

Abstract Photoemitted electron energy distributions from single crystals of Au at a photon energy of 16.8 eV are reported. Measurements have been taken for different surface orientations and electron emission angles. An anisotropic version of the three step model can describe the main features of the observed data.