1,5-Dimethyl-2,3,3,4-Tetrachloro-1,5-Diaza-2,4-Diphosphorinan-6-One and some derivatives

A synthesis of C-chlorinated analogues of 1,5-diaza-2,4-diphosphorinan-6-ones is described. The P-chlorophosphine 3 , a key compound for all reported substitution reactions, reacts in an unusual way with N,N′-dimethyl-N,N′-bis(trimethylsilyl)urea to give the unsymmetrical product 5 , the formation of which is accounted for by a silatropy of the intermediate compound 4 . Compound 5 is stable in solution but rearranges quantitatively into isomer 6 without solvent at room temperature. Compound 3 , its fluoro derivative 9 , and the alkoxy derivatives 10a–d exist as cis-and trans-isomers. Some stereochemical aspects, as well as the possibility of 1,2-chlorotropy, are discussed.     

Photoemission on a Cu-Zr glassy metal

In this paper we present a study of XPS, UPS and magnetic susceptibility on Cu₆₀·Zr₄₀ glassy metal. Our results can be understood in a band structure where the zirconium “d” levels lie close to the Fermi level meanwhile copper “d” levels are at higher binding energies; the density of states at the Fermi level is comparable to that of pure zirconium.     

Size-dependent grain-growth kinetics observed in nanocrystalline Fe

Measurements of grain growth in nanocrystalline Fe reveal a linear dependence of the grain size on annealing time, contradicting studies in coarser-grained materials, which find a parabolic (or power-law) dependence. When the grain size exceeds approximately 150 nm, a smooth transition from linear to nonlinear growth kinetics occurs, suggesting that the rate-controlling mechanism for grain growth depends on the grain size. The linear-stage growth rate agrees quantitatively with a model in which boundary migration is controlled by the redistribution of excess volume localized in the boundary cores.     

Magnetic interface polarization of the La-5d states in Fe/LaHx multilayers

For rare-earth (RE)-hydrides (REHx), a metal-to-insulator transition is observed if the hydrogen concentration is increased from the dihydride (x=2) towards the trihydride (x=3). This transition provides an object for studies of the magnetic interface polarization in layered ferromagnet/insulator structures. For different samples with a fixed Fe and varied LaH_x sublayer thickness t_LaHx ([15 ? Fe/t? LaH_x]xn), the H concentration x in the LaH_x sublayer is gradually increased in the experiment. Starting from the as prepared dihydride REH_2-δ, the modification of the magnetic polarization of the La-5d states at the Fe/La_x interface is studied across the transition by magnetic circular dichroism measurements at the La-L₂ and L₃ edges. The experiments reveal an induced magnetic polarization of the La-5d hole states on a length scale of 9 ? that is independent of the altered electronic structure of the La-5d states. Received: 23 May 2001 / Accepted: 4 July 2001 / Published online: 5 October 2001