Spin-reorientation in GdGa

We have determined the magnetic structure of the intermetallic compound GdGa by ¹⁵⁵Gd Mössbauer spectroscopy and neutron powder diffraction. This compound crystallizes in the orthorhombic (Cmcm) CrB-type structure. It orders ferromagnetically at T _c ?=?190(2) K and then undergoes a spin reorientation at T _SR ?=?68(2) K. Between T _c and T _SR , the magnetic structure is characterized by ferromagnetic order of the Gd moments along the b-axis. On cooling below T _SR , the Gd 4c magnetic moments split into two groups (2:2). At 3.6 K, the Gd moment is 6.7(4) μ _B , and the Gd magnetic moments are in the bc-plane, canted by 84(3)° and 46(4)° with respect to the crystallographic b-axis. This splitting into two magnetically inequivalent sites is confirmed by our 5 K ¹⁵⁵Gd Mössbauer results.     

Effects of Adsorbed Polyaniline on Redox Processes on As(2)O(3) Surfaces

Polyaniline deposited on As(2)O(3) surface resulted in a new material, which was characterized by infrared spectoscopy, thermogravimetry, differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and cyclic voltammetry. The mass percentage of polymer deposited on oxide surface is approximately 13%. The scanning electron microscopy images as well as the X-ray diffraction patterns provided conclusive evidence that the oxide surface is coated by the polymer. The cyclic voltammograms of the polyaniline adsorbed on As(2)O(3) surface showed that the adsorbate exerts remarkable effects on redox processes on this oxide. The pure oxide exhibited two oxidation/reduction peaks at 0.25/-0.06 and 0.47/-0.25 V attributed tentatively to the processes As(2)O(3)(s)+6H(+)+6e(-)=2As(s)+3H(2)O and As(s)+3H(+)+3e(-)=AsH(3)(g), respectively. The polyaniline-coated sample exhibited a better-defined voltammogram in which the first oxidation peak of the oxide had its intensity increased about four times. Copyright 2000 Academic Press.     

A Controlled Route to a Luminescent 3 d10–5 d10 Sulfido Cluster Containing Unique AuCu2(μ3‐S) Motifs

The first examples of gold(I) trimethylsilylchalcogenolate complexes were synthesized and their reactivity showcased in the preparation of a novel gold–copper–sulfur cluster [Au₄Cu₄S₄(dppm)₂] (dppm=bis(diphenylphosphino)methane). The unprecedented structural chemistry of this compound gives rise to interesting optoelectronic properties, including long‐lived orange luminescence in the solid state. Through time‐dependent density functional theory calculations, this emission is shown to originate from ligand‐to‐metal charge transfer facilitated by Au???Cu metallophilic bonding.