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

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"

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

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

Determination of the parameters characterizing the superexchange interaction in complex ferrite-spinels

A calculation procedure is proposed here for determining the values of exchange parameters, applicable to spinels which contain three kinds of ions in tetrahedral positions and which have an arbitrary distribution of cations. The values of exchange integrals obtained here for ferrites of the manganese-zinc system provide a useful basis for a quantitative interpretation of the spread of Curie-temperature readings in experiments which involve ferrites with the same composition. © 1976 Plenum Publishing Corporation

Magnetic microstructure in strontium hexaferrites with correlated nonisomorphous substitutions

The influence of the correlated nonisomorphous substitution of Mn2+ and Ti4+ ions for Fe3+ ions in M-type hexaferrites on the shaping of their magnetic microstructure is studied. Conclusions regarding the possibility of the distribution of the substituent cations in the structure and their influence on the principal magnetic properties of the hexaferrites studied are drawn on the basis of data from Mössbauer spectroscopy. © 1997 American Institute of Physics

Electrical and magnetic properties of lead-substituted lanthanum ferrimanganites

The temperature dependences of the electrical conductivity, thermopower, and magnetoresistance for single crystals of lead-substituted lanthanum ferrimanganites are investigated. The data on the magnetic microstructure obtained by Mössbauer spectroscopy are analyzed. An inversion of the magnetoresistance sign with an increase in temperature and the giant positive magnetoresistance are found for one of the samples. The magnetoresistance quadratically depends on the field, and its temperature dependence exhibits a maximum. © 2000 MAIK "Nauka/Interperiodica"

Mössbauer study of some perovskite-related oxides

Complex perovskite-related oxides with various structure types: orthoferrites, 4-1-5, 8-8-20, and 1-2-3 were studied using Mössbauer spectroscopy. Correlations between magnetic ordering of iron atoms and their structural coordination, as well as between oxygen deficiency and iron ion valence, were found. © 2006 by Allerton Press, Inc