High spin polarization at the interface between a Fe monolayer and InAs(110)

The magnetic and electronic properties of a Fe monolayer on InAs(110) are calculated with an ab initio method using the density-functional theory. We find that the relaxation of the InAs(110) surface is completely lifted and that the Fe atom is located in the center of the triangle formed of two As atoms and an adjacent In atom. The Fe bonding is largely determined by a molecularlike interaction of As and In orbitals with the Fe d levels. In particular, the density of states at the Fermi level is dominated by a bond between minority Fe d(xy), d(zy) levels and As p(x), In sp levels. This leads to a large value of 80% spin polarization on the Fe side and 60% on the InAs side of the interface albeit of different orientation. Into the crystal the spin-polarization exhibits a damped oscillation

STM measurements on the InAs(110) surface directly compared with surface electronic structure calculations

Ab initio density-functional-theory-local-density-approximation electronic structure calculations are performed for the InAs(110) surface and compared with scanning tunnel microscopy (STM) measurements using the Tersoff-Hamann model. In both, calculations and measurements, we see the same atomic features. At negative and small positive energies, the local density of states is concentrated around the As atom, while at higher positive energies it is centered above the In atom, because of the appearance of the In dangling bond. Moreover, we describe two types of irregular STM images on the InAs(110) surface. First, we measure dI/dV images exhibiting atomic resolution at voltages within the band gap, which, however, still can be understood within the Tersoff-Hamann model as due to a higher-order term. Second, we measure features on the subatomic scale with certain tips at low tip-sample distance, which are most likely caused by elastic interactions between the tip and the surface

Scanning tunneling spectroscopy on Co(0001):Spectroscopic signature of stacking faults and dislocation lines

The growth morphology and electronic structure of Co(0001) grown on W(110) are studied using scanning tunneling microscopy and scanning tunneling spectroscopy (STS) at T=6 K. Depending on growth conditions, continuous Co films or Co islands on top of a wetting layer are formed. Within the continuous films, dislocation lines appear and increase in density after annealing. Co islands and films exhibit dI/dV curves with a pronounced peak at -0.3 eV below the Fermi energy. The intensity of this peak is changing in different areas of the surface. Using monolayer high islands with a different shape deposited on the same Co layer we attribute the different intensity to a different stacking of the Co surface. The change in intensity is reproduced by first-principles electronic structure calculations, which reveal that the peak is caused by a d(3z)(2)-r(2)-like surface resonance of a minority-spin character more strongly coupled to the bulk states in the case of hcp (ABA) stacking than in the case of fcc (ABC) stacking. An increased STS intensity of the surface resonance was also found above dislocation lines located at the Co/W interface

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Anisotropic superexchange in one-dimensional Fe-chains on InAs(110)

The magnetic and electronic properties of Fe chains on InAs(I 10) are calculated from first-principles using the density functional theory. The magnetic ground state is found to be anti ferromagnetic (AF) for Fe chains along [1-10] direction and ferromagnetic (FM) for Fe chains along the perpendicular [001] direction. The AF structure is explained with an AF superexchange between Fe atoms via mediating As, while the FM structure is explained with a more complicated exchange path via surface As and In atoms. (c) 2008 Elsevier B.V. All rights reserved