執筆者紹介

It is established that the average (over the number of bonds) intensity of the superexchange interaction of the Fe**3** plus ion with magnetic neighbors decreases by 10% on replacement of one oxygen ion with a fluorine ion, irrespective of the nature of the cation substitution

Thermal analysis, thermal expansion of Pr[1–x]La[x]InO[3] praseodymium-lanthanum indates

Praseodymium, lanthanum indates solid solutions Pr[1–x]La[x]InO[3] were synthesized by ceramic method for the first time. It was found that in PrInO[3] – LaInO[3] binary system there was a continuous range of praseodymium-lanthanum indates solid solutions Pr[1–x]La[x]InO[3] with the structure of orthorhombically distorted perovskite. Thermal elongation of synthesized samples was investigated in 400–1,120 K temperature range. Сomplex thermal analysis of the samples synthesized was carried out up to 1,273 K. Temperature dependences of relative elongation had no anomalies due to the phase transitions and using these dependences average linear coefficients of thermal elongation were calculated by leastsquares technique. On the differential scanning calorimetry (DSC) curves for all the samples investigated no thermal effects were observed

Synthesis of the aluminum-substituted hexaferrite SrFe 9.5Al 2.5O 19

The phase-formation processes involved in the synthesis of the hexagonal ferrite SrFe 9.5Al 2.5O 19 by solid-state reaction at 900°C for 5 min to 8 h were studied by x-ray diffraction and Mössbauer spectroscopy. The formation of the hexagonal ferrite at this temperature was found to take 3 h. The resultant material also contained SrAl 2O 4 and SrFeO 3-x, which suggests that, for the synthesis to reach completion, the heat-treatment temperature should be higher. The aluminum cations in the hexaferrite phase were shown to occupy, for the most part, positions 12k and 4f 1. © 1999 MAHK "Hayka/Interperiodica"

Physical and chemical properties of Bi[1–x]La[x]Fe[1–x]Co[x]O[3] solid solutions synthesized by different methods

By using solid-state and sol-gel technologies solid solutions of the BiFeO[3] – LaCoO[3] system were synthesized. The parameters of their crystal lattice were determined. The temperature dependence of electrical conductivity and thermal expansion of the Bi[1–x]La[x]Fe[1–x]Co[x]O[3](x = 0, 0.05, 0.1, 1.0) samples was studied in air in the temperature range of 300–1,050 K. It was shown that the use of sol-gel technology reduces the temperature and the time of synthesis. The samples obtained by solid-phase method have lower coefficients of thermal expansion and specific conductivity

Long-range attraction between particles in dusty plasma and partial surface tension of dusty phase boundary

Effective potential of a charged dusty particle moving in homogeneous plasma has a negative part that provides attraction between similarly charged dusty particles. A depth of this potential well is great enough to ensure both stability of crystal structure of dusty plasma and sizable value of surface tension of a boundary surface of dusty region. The latter depends on the orientation of the surface relative to the counter-ion flow, namely, it is maximal and positive for the surface normal to the flow and minimal and negative for the surface along the flow. For the most cases of dusty plasma in a gas discharge, a value of the first of them is more than sufficient to ensure stability of lenticular dusty phase void oriented across the counter-ion flow.Comment: LATEX, REVTEX4, 7 pages, 6 figure

New and old N=8 superconformal field theories in three dimensions

We show that an infinite family of N=6 d=3 superconformal Chern-Simons-matter theories has hidden N=8 superconformal symmetry and hidden parity on the quantum level. This family of theories is different from the one found by Aharony, Bergman, Jafferis and Maldacena, as well as from the theories constructed by Bagger and Lambert, and Gustavsson. We also test several conjectural dualities between BLG theories and ABJ theories by comparing superconformal indices of these theories.Comment: 16 pages, late

Magnetic properties of solid solutions of BiFeO3– SmCoO3 system

Solid solutions of BiFeO3– SmCoO3were synthesized by a solid-state method. Peculiarities of the influence of isovalent substitution of Bi 3+ and Fe 3+ ions in BiFeO3by Sm 3+ , Co 3+ ions on the crystal structure and magnetic properties of Bi1–xSmxFe1–xCoxO3solid solutions are found. It is shown that the substitution 3-25% of the Bi 3+ , Fe 3+ ions in BiFe0O3by Sm 3+ , Co 3+ ions results in the gradual destruction of the antiferromagnetic and conception of ferromagnetic ordering. In this case replacing up to 10% of Sm 3+ and Co 3+ ions in SmCoO3by Bi 3+ and Fe 3+ ions leads to the stabilization of Co 3+ ions in a diamagnetic state

Crystal structure and magnetic properties of highly-coercive Sr[1–x]Gd[x]Fe[12–x]Zn[x]O[19] ferrites

High-coercivity ferrite samples Sr[1–x]Gd[x]Fe[12–x]Zn[x]O]19] (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) with magnetoplumbite structure were prepared from oxides Fe[2]O[3], Gd[2]O[3], ZnO and carbonate SrCO[3] by solid-state ceramic method, the dependence of the unit cell parameters aand con the value of xwas determined. XRD showed that the samples with x >0.1 were not single-phase, and the samples with x > 0.2 contained not only bases phase with the structure of magnetplumbite, but also the a-Fe[2]O[3] and Gd[3]Fe[5]O[12] phases. It was found that increase of the xvalue leads to a slight decrease in the Curie temperature (from 727 K for the basic ferrite SrFe[12]O[19] to 714 K for Sr[1–x]Gd[x]Fe[12–x]Zn[x]O[19] solid solution with x = 0.5). It has been found that at 300 K values of spontaneous magnetization (no) and coercive force (?Hc) of solid solution Sr[0.9]Gd[0.1]Fe[11.9]Zn[0.1]O[19] are respectively 1.3 and 2.3% higher than for the base ferrite SrFe[12]O[19], and values of samples with x > 0.1 of these magnetic properties decreases gradually

CHARACTERISTICS OF SUPEREXCHANGE INTERACTIONS IN FLUORINE-SUBSTITUTED FERRITES.

It is established that the average (over the number of bonds) intensity of the superexchange interaction of the Fe**3** plus ion with magnetic neighbors decreases by 10% on replacement of one oxygen ion with a fluorine ion, irrespective of the nature of the cation substitution

Maximum Renyi entropy principle for systems with power--law Hamiltonian

The Renyi distribution ensuring the maximum of a Renyi entropy is investigated for a particular case of a power--law Hamiltonian. Both Lagrange parameters, $\alpha$ and $\beta$ can be excluded. It is found that $\beta$ does not depend on a Renyi parameter $q$ and can be expressed in terms of an exponent $\kappa$ of the power--law Hamiltonian and an average energy $U$. The Renyi entropy for the resulted Renyi distribution reaches its maximal value at $q=1/(1+\kappa)$ that can be considered as the most probable value of $q$ when we have no additional information on behaviour of the stochastic process. The Renyi distribution for such $q$ becomes a power--law distribution with the exponent $-(\kappa +1)$. When $q=1/(1+\kappa)+\epsilon$ ($0<\epsilon\ll 1$) there appears a horizontal "head" part of the Renyi distribution that precedes the power--law part. Such a picture corresponds to observables.Comment: LaTeX, 7 pages, 4 figure