Successful grafting of isolated molecular Cr7Ni rings on Au(111) surface

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Antiferromagnetic coupling of TbPc2 molecules to ultrathin Ni and Co films

The magnetic and electronic properties of single-molecule magnets are studied by X-ray absorption spectroscopy and X-ray magnetic circular dichroism. We study the magnetic coupling of ultrathin Co and Ni films that are epitaxially grown onto a Cu(100) substrate, to an in situ deposited submonolayer of TbPc2 molecules. Because of the element specificity of the X-ray absorption spectroscopy we are able to individually determine the field dependence of the magnetization of the Tb ions and the Ni or Co film. On both substrates the TbPc2 molecules couple antiferromagnetically to the ferromagnetic films, which is possibly due to a super-exchange interaction via the phthalocyanine ligand that contacts the magnetic surface

Spin-communication channels between Ln(III) bis-phthalocyanines molecular nanomagnets and a magnetic substrate

Learning the art of exploiting the interplay between different units at the atomic scale is a fundamental step in the realization of functional nano-architectures and interfaces. In this context, understanding and controlling the magnetic coupling between molecular centers and their environment is still a challenging task. Here we present a combined experimental-theoretical work on the prototypical case of the bis(phthalocyaninato)-lanthanide(III) (LnPc$_{2}$) molecular nanomagnets magnetically coupled to a Ni substrate. By means of X-ray magnetic circular dichroism we show how the coupling strength can be tuned by changing the Ln ion. The microscopic parameters of the system are determined by ab-initio calculations and then used in a spin Hamiltonian approach to interpret the experimental data. By this combined approach we identify the features of the spin communication channel: the spin path is first realized by the mediation of the external (5d) electrons of the Ln ion, keeping the characteristic features of the inner 4 f orbitals unaffected, then through the organic ligand, acting as a bridge to the external world

VIBRATIONAL AND COLLECTIVE EXCITATIONS OF THE CS/GAAS(110) INTERFACE

We present a high-resolution electron-energy-loss analysis of the interface system Cs/GaAs(110) grown at room temperature. We study the development of the GaAs collective excitation features (Fuchs-Kliewer surface phonon and plasmon of the dopant-induced free carriers) as a function of the alkali-metal deposition. An energy-loss structure at about 8 meV is inferred by a detailed data analysis, that we attribute to a Cs-induced excitation. By using an appropriate dielectric model applied to our data, Cs does not form a uniform metallic layer at saturation coverage, while it cannot be ruled out that it forms metallic clusters of a few tens of angstrom in size. Cs deposition is known to produce a band bending at the (I 10) surface of GaAs. Using a semiclassical model for interpreting the energy and intensity modifications of the plasmon and phonon modes, we also deduced the widening of the depletion layer due to the adsorbate. We then obtained a band bending of 0.73 eV for the n-type doped substrate, in good agreement with previous results. We remark that this indirect method for determining the band bending is not affected by any surface photovoltage effects

COLLECTIVE AND VIBRATIONAL EXCITATIONS ON THE N-DOPED GAAS(110) SURFACE

A detailed high-resolution electron-energy-loss-spectroscopy study of the surface collective and vibrational excitations of the clean n-doped GaAs(110) cleaved surface is presented. Measurements were taken exploiting a wide range of primary-beam energy and at two different dopant concentrations. Due to their coupling in the sample with higher doping, both the free-carrier plasmon and the Fuchs-Kliewer mode show dispersion. The phonon intensity behavior, when the primary-beam energy is changed, is opposite to that of the plasmon. The intensity behavior of the latter mode, in particular, suggests its spatial confinement beneath the surface. © 1989 The American Physical Society