Polarized neutron reflectometry of Fe/Cr/Gd superlattices

The magnetic structure of Fe/Cr/Gd superlattices is investigated using complementary methods of SQUID magnetometry and polarized neutron reflectometry. The complex magnetic behavior of the given system is caused by exchange interaction between the 3d (Fe) and 4f (Gd) layers of the ferromagnetic metals through the Cr antiferromagnetic spacer layer. It is found that a nonuniform profile of magnetization forms within the Gd layers under the influence of this interlayer interaction.     

Synthesis of 4-alkylthio-2-(o-hydroxyphenyl)-1,3,5-triazines by recyclization of 4-oxo-1,3-benzoxazine perchlorates

A method has been developed for synthesis of 4-alkylthio-2-(o-hydroxyphenyl)-1,3,5-triazines by treatment of 4-oxo-1,3-benzoxazine perchlorates with S-methyl, benzyl, and allyl-isothioureas.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1658–1661, December, 1989.     

Synthesis of 4-oxo-1,3-benz- and naphthoxazinium salts from o-hydroxyarylamides

The acid-catalyzed acylation of primary and secondary o-hydroxyarylamides, the probable reaction scheme, and the possibility of the formation of 4-oxo-1,3-arenooxazinium salts and analogs in the reaction of amides of salicylic, coumaric, and 1-hydroxy- and 3-hydroxynaphthoic acids and their N-alkyl(aryl)derivatives with excess amounts of aliphatic acid anhydrides and 70% perchloric acid, as well as by the acid cyclization of O- and N-mono- and diacyl derivatives of these amides, are examined. Twelve previously unknown 2-alkyl- and 2-styryl-4-oxo-1,3-naphth[3,2-e]-and -[1,2-e]oxazinium perchlorates were synthesized. N-Methyl- and N-benzylamides of 8-acetoxy-1-naphthoic acid are formed instead of the expected peri-cyclic analogs of oxazinium salts in the reaction of 8-hydroxy-1-naphthoic acid anilides with acetic anhydride and perchloric acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1611–1616, December, 1979.Original article submitted May 31, 1978; revision submitted April 2, 1979.     

Radiochemical characterization and decontamination of rare-earth-element concentrate recovered from uranium leach liquors

Journal of Radioanalytical and Nuclear Chemistry - The paper deals with two rare earth elements (REE) concentrates recovered from uranium leach liquors after sorption separation of uranium....     

Reaction of 4H-1, 3-benzoxazine-4-onium salts with C-nucleophilic aromatic compounds

A method is proposed for the synthesis of 2-(4-dialkylaminophenyl)-2,3-dihydro-4H-1,3-benzoxazin-4-ones and diindolylcyaninemethanes by reaction of 4H-1,3-benzoxazin-4-onium salts with N,N-dialkylanilines and indole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 47–50, January, 1977.     

Temperature and concentration dependences of the electrical resistivity for alloys of plutonium with americium under normal conditions

The temperature and concentration dependences of the electrical resistivity for alloys of americium with plutonium are analyzed in terms of the multiband conductivity model for binary disordered substitution-type alloys. For the case of high temperatures (T > Θ_D, Θ_D is the Debye temperature), a system of self-consistent equations of the coherent potential approximation has been derived for the scattering of conduction electrons by impurities and phonons without any constraints on the interaction intensity. The definitions of the shift and broadening operator for a single-electron level are used to show qualitatively and quantitatively that the pattern of the temperature dependence of the electrical resistivity for alloys is determined by the balance between the coherent and incoherent contributions to the electron-phonon scattering and that the interference conduction electron scattering mechanism can be the main cause of the negative temperature coefficient of resistivity observed in some alloys involving actinides. It is shown that the great values of the observed resistivity may be attributable to interband transitions of charge carriers and renormalization of their effective mass through strong s-d band hybridization. The concentration and temperature dependences of the resistivity for alloys of plutonium and americium calculated in terms of the derived conductivity model are compared with the available experimental data.     

Temperature and concentration dependences of the plutonium-americium alloy resistivity at high temperatures

A many-band model of conductivity is stated in terms of which it is shown qualitatively and quantitatively that interference scattering of conduction electrons may be the main reason for the negative temperature coefficient of resistance in actinide alloys at high temperatures (T > Θ_D). The temperature run of the resistivity in such alloys is completely determined by the balance between coherent and incoherent contributions to electron-impurity-phonon scattering. The model is used to analyze the concentration and temperature dependences of the plutonium and americium alloy resistivity.     

Coherent Fan Magnetic Structure in Dy/Gd Superlattices

The magnetic structure of pseudo-single-crystal (0001) Dy/Gd superlattices, as well as its modification with the temperature, is determined by the combined application of SQUID magnetometry, circular magnetic dichroism, and polarized neutron reflectometry. It is established that a fan magnetic order is formed in the Dy layers in relatively low magnetic fields at temperatures below 170 K. Then, this order propagates coherently throughout the superlattice. The magnetic moments in the Dy layers lie in the basal plane, and in the Gd layers, they are oriented mainly along the hexagonal c axis.