Chemistry of indole

Condensation of 1-alkyl-2-aminoindoles with malonic ester gives -carbonyl derivatives which, on the basis of the their UV, IR, and NMR spectra, and their chemical properties, are assigned the 2-oxo-4-hydroxy--carboline structure.For Part XVIII, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1207–1211, September, 1970.     

Perpendicular exchange bias and its control by magnetic,stress and electric fields

Perpendicular exchange bias (PEB) involving perpendicular magnetic anisotropy (PMA) in both the antiferromagnetic (AF) pinning and the ferromagnetic (FM) sensor layer is expected to become important in future perpendicular recording and sensing devices. Further, because of the reduced spin dimensionality, PEB promises to be easier understandable than the conventional planar exchange bias (EB). In addition to its first realization using the Ising-type AF compounds FeF2 and FeCl2 we have tested control strategies of EB being alternative to the conventional magnetic and thermal ones. Indeed, specific symmetry properties of the pinning layer have been shown to enable mechanical (viz. piezomagnetic via FeF2) and electric control (viz. magneto-electric via Cr2O3) of EB, respectively. Electric control promises to become relevant for TMR devices in MRAM technology.     

Magnetoelectric switching of exchange bias

The perpendicular exchange bias field, H(EB), of the magnetoelectric heterostructure Cr2O3(111)/(Co/Pt)(3) changes sign after field cooling to below the Néel temperature of Cr2O3 in either parallel or antiparallel axial magnetic and electric freezing fields. The switching of H(EB) is explained by magnetoelectrically induced antiferromagnetic single domains which extend to the interface, where the direction of their end spins controls the sign of H(EB). Novel applications in magnetoelectronic devices seem possible.     

Impurity-induced localisation of the 2D surface-state continuum on a metal surface

The local density of states of two model systems formed by an individual adsorbate (Cs or Ar) on a Cu(111) surface is investigated using a wave-packet propagation approach. In both cases a sharp peak appears at the threshold of the 2D Shockley surface-state continuum. This peak is attributed to quasi-stationary states located just below the 2D continuum. Following the existence criterion for a bound state in two dimensions by Simon, such states splitting off the surface-state bottom should appear whenever the surface-state continuum is perturbed by an attractive potential, independently of the existence of atomic-like states bound by the perturbing potential. These findings are discussed in connection with recent observations of peaks located at the surface-state threshold in scanning tunnelling microscopy experiments. PACS 68.37.Ef; 73.20.At; 73.20.Hb; 68.43.-h