The distribution of ions and their valencies in manganese ferrites I. MnFe2O4+γ ferrites

A model for the distribution of cations in the spinel lattice of manganese ferrites MnFe₂O₄₊ was elaborated on the basis of the experimental studies of the basic magnetic quantities, electrical conductivity and magnetic relaxation of the given ferrites, taking into consideration their crystallographic properties. The conclusions following from this model are in good agreement with the experimental results obtained by us and by other authors both for stoichiometric manganese ferrite and for a ferrite where 0.

---

I. MnFe₂O₄₊

, MnFe₂O₄₊ . , , , , , 0.

     

Measurement of vapor-liquid equilibrium in systems with components of very different volatility by the total pressure static method

To make feasible the experimental study of vapor-liquid equilibrium (VLE) in the systems mentioned in the title, a static apparatus for accurate measurement of total vapor pressures of solutions was constructed. Mixtures of known composition are prepared synthetically in a thermostated equilibrium cell by weight from pure degassed components and the total pressure is measured by a quartz Bourdon gage. A procedure was developed for degassing pure liquids to a degree corresponding to the high precision of pressure determination required. The static assembly was tested by comparing obtained isothermal vapor pressures and calculated excess Gibbs free energies with literature data for the benzene - cyclohexane system at 14 and 20°C, respectively. Additional experimental vapor-pressure data are presented for pure cyclohexane, benzene, and N-methylpyrrolidone (abbreviated throughout this paper as NMP) at 6–24°C and for the binary systems of benzene-cyclohexane at 8°C and cyclohexane - NMP and benzene - NMP at 8, 14, and 20°C over the entire composition range. The binary data were reduced by a modified Barker's method to evaluate excess Gibbs free energies and vapor phase compositions.     

Internal strain parameter of silicon and GaAs and planar force constants

We show that the internal strain parameter ζ and elastic constants of the tetrahedral semiconductors can be determined from the force constants between planes of atoms. These have been computed recently for Si and GaAs from self-consistent electronic calculations using the Hellmann-Feynman theorem. The theoretical results are ζ = 0.72 for GaAs and ～0.57 for Si compared to experimental values of 0.76 and 0.73.     

Новый метод измерени я магнитокалорическ ого эффекта у ферромагни тных полупроводнико в

, .     

Vibration of ionic crystals containing substitutional defects in the shell model

Formulae for calculation of the local modes and of the Green function of defect lattices can be simplified if the matrix characterising the defect is singular. From this point of view are investigated vibrations of an ionic crystal containing a substitutional defect the charge of which is equal to the charge of the substituted ion.     

Влияние матерала ано да на формирование положителъного стол ба тлеющего разряда

---

The influence of anode material on the forming of a positive column in a glow discharge

     

ПРИГОТОВЛЕНИЕ И ХАРА КТЕР ПОВЕРХНОСТИ ПЛАСТИНОК AgBr

AgBr . , .