Theory of transverse spin dynamics in a polarized Fermi liquid and an itinerant ferromagnet

The linear equations for transverse spin dynamics in a weakly polarized degenerate Fermi liquid with arbitrary relationship between temperature and polarization are derived from Landau-Silin phenomenological kinetic equation with general form of two-particle collision integral. Unlike the previous treatment where Fermi velocity and density of states have been taken as constants independent of polarization here we made derivation free from this assumption. The obtained equations are applicable for description of spin dynamics in paramagnetic Fermi liquid with finite polarization as well in an itinerant ferromagnet. In both cases transverse spin wave frequency is found to be proportional to the square of the wave vector with complex constant of proportionality (diffusion coefficient) such that the damping has a finite value at T=0. The polarization dependence of the diffusion coefficient is found to be different for a polarized Fermi liquid and for an itinerant ferromagnet. These conclusions are confirmed by derivation of transverse spin wave dispersion law in frame of field theoretical methods from the integral equation for the vortex function. It is shown that similar derivation taking into consideration the divergency of static transverse susceptibility also leads to the same attenuating spin wave spectrum.Comment: 7 pages, no figure

Способ работы паротурбинной установки в нестационарных режимах

While starting turbines from cold and non-cooled-down states rotors are heated quicker than cylinders due to significantly less weight and more intensive interaction with steam and the value of their differential expansion reaches up to the rated ones in the period of 4-5 hours.The investigations have revealed that while using a swirling steam attemperator it is possible to feed steam to turbine seals of the required temperature and at the required time during its variable operational conditions. This methodology makes it possible to save 400 t of specific fuel. In addition to this operational reliability of a power block is increased and a number and cost of repairs is decreased.При пуске турбин из холодного и неостывшего состояний роторы из-за значительно меньшей массы и более интенсивного взаимодействия с паром нагреваются быстрее цилиндров и через 4–5 ч величина их относительного расширения доходит до предельно допустимых значений.Исследования показали, что только при использовании вихревого пароохладителя можно подавать пар нужной температуры и в нужное время на уплотнения турбины при ее переменных режимах работы, благодаря чему ее пуск ускоряется на 5 ч. Это приводит к экономии около 400 т у. т. в год. Кроме того, возрастает надежность работы энергоблока и уменьшаются количество и стоимость ремонтов

Spin Wave Theory of Double Exchange Ferromagnets

We construct the 1/S spin-wave expansion for double exchange ferromagnets at T=0. It is assumed that the value of Hund's rule coupling, J_H, is sufficiently large, resulting in a fully saturated, ferromagnetic half-metallic ground state. We evaluate corrections to the magnon dispersion law, and we also find that, in contrast to earlier statements in the literature, magnon-electron scattering does give rise to spin wave damping. We analyse the momentum dependence of these quantities and discuss the experimental implications for colossal magnetoresistance compounds.Comment: 4 pages, Latex-Revtex, 2 PostScript figures. Minor revisions, references added. See also cond-mat/990921

Spin-wave Scattering in the Effective Lagrangian Perspective

Nonrelativistic systems exhibiting collective magnetic behavior are analyzed in the framework of effective Lagrangians. The method, formulating the dynamics in terms of Goldstone bosons, allows to investigate the consequences of spontaneous symmetry breaking from a unified point of view. Low energy theorems concerning spin-wave scattering in ferro- and antiferromagnets are established, emphasizing the simplicity of actual calculations. The present work includes approximate symmetries and discusses the modification of the low energy structure imposed by an external magnetic and an anisotropy field, respectively. Throughout the paper, analogies between condensed matter physics and Lorentz-invariant theories are pointed out, demonstrating the universal feature of the effective Lagrangian technique.Comment: Published versio

Повышение эффективности работы конденсатора

A system of modernized capacitor ball-cleaning that prevents formation of depositions on internal capacitor tube surface has been developed in the paper.The system has been introduced at the Minsk TPP-4 (Power Block No.5). The paper presupposes that the economic effect will be nearly 0.43 million US dollars per year at one poer block with turbine Т-250/300-240.Разработана система модернизированной шарикоочистки конденсатора, препятствующая образованию отложений на внутренней поверхности трубок конденсатора.Система внедрена на Минской ТЭЦ-4 (энергоблок № 5). Предполагается, что экономический эффект составит около 0,43 млн дол. в год на одном энергоблоке с турбиной Т-250/300-240