Nanoferroics: state of art, gradient driven couplings and advanced applications (Authors' review)

Ferroics and multiferroics are unique objects for fundamental physical research of complex nonlinear processes and phenomena, which occur in them in micro and nanoscale. Due to the possibility of their physical properties control by size effects, nanostructured and nanosized ferroics are among the most promising for advanced applications in nanoelectronics, nanoelectromechanics, optoelectronics, nonlinear optics and information technologies. The review discuss and analyze that the thickness of the strained films, the size and shape of the ferroic and multiferroic nanoparticles are unique tools for controlling their phase diagrams, long range order parameters, magnitude of susceptibility, magnetoelectric coupling and domain structure characteristics at fixed temperature. Significant influence of the flexochemical effect on the phase transition temperature, polar and dielectric properties is revealed for thin films and nanoparticles. Obtained results are important for understanding of the nonlinear physical processes in nanoferroics as well as for the advanced applications in nanoelectronics.Comment: 23 pages, 15 figure

Defect driven flexo-chemical coupling in thin ferroelectric films

Using Landau-Ginzburg-Devonshire theory, we considered the impact of the flexoelectro-chemical coupling on the size effects inpolar properties and phase transitions of thin ferroelectric films with a layer of elastic defects. We investigated a typical case, when defects fill a thin layer below the top film surface with a constant concentration creating an additional gradient of elastic fields. The defective surface of the film is not covered with an electrode, but instead with an ultra-thin layer of ambient screening charges, characterized by a surface screening length. This geometry is typical for the scanning probe piezoelectric force microscopy. Obtained results revealed an unexpectedly strong effect of the joint action of Vegard stresses and flexoelectric effect (shortly flexo-chemical coupling) on the ferroelectric transition temperature, distribution of the spontaneous polarization and elastic fields, domain wall structure and period in thin PbTiO3 films containing a layer of elastic defects. A nontrivial result is the ferroelectricity persisting at film thicknesses below 4 nm, temperatures lower than 350 K and relatively high surface screening length (~0.1 nm). The origin of this phenomenon is the re-building of the domain structure in the film (namely the cross-over from c-domain stripes to a-type closure domains) when its thickness decreases below 4 nm, conditioned by the flexoelectric coupling and facilitated by negative Vegard effect. For positive Vegard effect, thicker films exhibit the appearance of pronounced maxima on the thickness dependence of the transition temperature, whose position and height can be controlled by the defect type and concentration. The revealed features may have important implications for miniaturization of ferroelectric-based devices.Comment: 25 pages, 9 figure

Fixed Volume Effect on Polar Properties and Phase Diagrams of Ferroelectric Semi-ellipsoidal Nanoparticles

For advanced applications in modern industry it is very important to reduce the volume of ferroelectric nanoparticles without serious deterioration of their polar properties. In many practically important cases fixed volume (rather than fixed size) corresponds to realistic technological conditions of nanoparticles fabrication. The letter is focused on the theoretical study of the behavior of ferroelectric polarization, paramagnetoelectric coefficient and phase diagrams of semi-ellipsoidal nanoparticles with fixed volume V. Our approach combines the Landau-Ginzburg-Devonshire phenomenology, classical electrostatics and elasticity theory. Our results show that the size effects of the phase diagrams and polarization of semi-ellipsoidal BiFeO3 nanoparticles nontrivially depends on V. These findings provide a path to optimize the polar properties of nanoparticles by controlling their phase diagrams at a fixed volume.Comment: 15 pages, 5 figures, we added the section IV. Paramagnetoelectric (PME) coefficient at fixed volume in this version and changed title and abstract accordingl

Self-consistent theory of nanodomain formation on nonpolar surfaces of ferroelectrics

We propose a self-consistent theoretical approach capable to describe the peculiarities of the anisotropic nanodomain formation induced by a charged AFM probe on non-polar cuts of ferroelectrics. The proposed semi-phenomenological approach accounts for the difference of the threshold fields required for the domain wall motion along non-polar X- and Y - cuts, and polar Z - cut of LiNbO3. The effect steams from the fact, that the minimal distance between the equilibrium atomic positions of domain wall and the profile of lattice pinning barrier appeared different for different directions due to the crystallographic anisotropy. Using relaxation-type equation with cubic nonlinearity we calculated the polarization reversal dynamics during the probe-induced nanodomain formation for different threshold field values. The different velocity of domain growth and consequently equilibrium domain sizes on X-, Y- and Z-cuts of LiNbO3 originate from the anisotropy of the threshold field. Note that the smaller is the threshold field the larger are the domain sizes, and the fact allows explaining several times difference in nanodomain length experimentally observed on X- and Y-cuts of LiNbO3. Obtained results can give insight into the nanoscale anisotropic dynamics of polarization reversal in strongly inhomogeneous electric field.Comment: 22 pages, 8 figure

Ferromagnetic-like behavior of Bi0.9La0.1FeO3-KBr nanocomposites

We studied magnetostatic response of the Bi0.9La0.1FeO3-KBr composites (BLFO-KBr) consisting of nanosized (about 100 nm) ferrite Bi0.9La0.1FeO3 (BLFO) conjugated with fine grinded ionic conducting KBr. When the fraction of KBr is rather small (less than 15 wt percent) the magnetic response of the composite is very weak and similar to that observed for the BLFO (pure KBr matrix without Bi1-xLaxFeO3 has no magnetic response as anticipated). However, when the fraction of KBr increases above 15percent, the magnetic response of the composite changes substantially and the field dependence of magnetization reveals ferromagnetic-like hysteresis loop with a remanent magnetization about 0.14 emu/g and coercive field about 1.8 Tesla (at room temperature). Nothing similar to the ferromagnetic-like hysteresis loop can be observed in BLFO ceramics, which magnetization quasi linearly increases with magnetic field. Different physical mechanisms were considered to explain the unusual experimental results for BLFO-KBr nanocomposites, but only those among them, which are highly sensitive to the interaction of antiferromagnetic Bi0.9La0.1FeO3 with ionic conductor KBr, can be relevant. An appropriate mechanism turned out to be ferro-magneto-ionic coupling.Comment: 24 pages, 4 figures in the main text, and supplement with 4 figure

ІНФОРМАЦІЙНІ АСПЕКТИ ВПРОВАДЖЕННЯ СИСТЕМИ ЕНЕРГОМЕНЕДЖМЕНТУ «КОНТРОЛЬ І ПЛАНУВАННЯ ЕНЕРГОСПОЖИВАННЯ» НА КОТЕЛЬНИХ ЦСТ

The data of the daily statements of the operation of the equipment of 11 boiler houses are analyzed. Coefficient of efficiency On the direct balance is not determined anywhere, therefore it is impossible to evaluate the reliability of the information; If the coefficient of efficiency Determine by (1), it turns out that boiler No. 1 of the boiler house X-quarter YUZM on January 14, 2013, most of the time worked with the coefficient of efficiency 0,95-1,01, and boiler No. 2 worked for a whole day with coefficient of efficiency 1.21. The check for this day in the boiler's daily statement shows the error of the records, which is detected and taken into account when modelling in the technical inspection. A comparison of the adjusted coefficient of efficiency is made on the direct balance sheet with the data of the daily modelling of the energy conversion carried out by the enterprise's technical inspection. Errors in the determination of coefficient of efficiency are considered on the direct balance sheet and the possibility of using the corrected daily log data of the operator's log for monitoring energy efficiency indicators through coefficient of efficiency measures and through the specific gas consumption for heat production. A regression analysis of the quality of heat management and weather regulation is described. The Energy Management Service launched an energy monitoring program for all fuel and energy resources in the city's district and quarter boiler houses. The program allows to determine the efficiency of the boiler house on the basis of an electronic sheet. With the assistance of thermal automation and measurement services, information technology a program was developed and launched. The program allow to operative boiler room personnel to track the efficiency operation of boilers in real time It will allow to determine the efficiency of boiler operation regulation in practice by the operating personnel of boiler houses.Проанализированы данные суточных ведомостей работы оборудования 11 котельных; к.п.д. по прямому балансу нигде не определяется, поэтому оценить достоверность информации нельзя; если к.п.д. определить по (1), то окажется, что котел №1 котельной Х-квартал 14 января 2013 г. большую часть времени суток работал с к.п.д. 0,95-1,01, а котел № 2 целые сутки проработал с к.п.д. 1,21. Проверка для этого дня в суточной ведомости котельной показывает ошибочность записей, что обнаруживают  и учитывают при макетировании в ПТО.  Проведено сравнение скорректированного к.п.д. по прямому балансу с данными посуточного макетирования преобразования энергии, выполняемого ПТО предприятия. Рассмотрены погрешности  определения к.п.д. по прямому балансу и возможность использования скорректированных данных суточной ведомости журнала оператора для мониторинга показателей энергоэффективности через к.п.д. и через удельный расход газа на выработку тепла.  Описан регрессионный анализ качества управления отпуском теплоты и погодным регулированием. Службой энергетического менеджмента запущенна программа энергетического мониторинга всех ТЭР по районным и квартальным котельным города;  программа позволяет на основании электронной ведомости определить эффективность работы котельной.  При содействии служб тепловой автоматики и измерений, информационных технологий была разработана и запущенна программа, позволяющая оперативному персоналу котельных отслеживать к.п.д.  работы котлов в реальном времени, что на практике позволит определить эффективность регулирования работы котлов оперативным персоналом котельных.Проаналізовано дані добових відомостей роботи обладнання 11 котелень; к.к.д. за прямим балансом ніде не визначається, тому оцінити достовірність інформації не можна; якщо к.к.д. визначити по (1), то виявиться, що котел №1 котельні Х-квартал 14 січня 2013 р більшу частину часу доби працював з к.к.д. 0,95-1,01, а котел № 2 цілу добу пропрацював з к.к.д. 1,21. Перевірка для цього дня в добовій відомості котельні показує хибність записів, що виявляють і враховують при макетування в ПТО. Проведено порівняння скоригованого к.к.д. за прямим балансом з даними добового макетування перетворення енергії, що виконується ПТО підприємства. Розглянуто похибки визначення к.к.д. за прямим балансом і можливість використання скоригованих даних добової відомості журналу оператора для моніторингу показників енергоефективності через к.к.д. і через питома витрата газу на вироблення тепла. Описано регресійний аналіз якості управління відпуском теплоти і погодним регулюванням. Службою енергетичного менеджменту запущена програма енергетичного моніторингу всіх ПЕР по районним та квартальним котельним міста; програма дозволяє на підставі електронної відомості визначити ефективність роботи котельні. За сприяння служб теплової автоматики і вимірювань, інформаційних технологій була розроблена і запущена програма, що дозволяє оперативному персоналу котелень відстежувати к.к.д. роботи котлів в реальному часі, що на практиці дозволить визначити ефективність регулювання роботи котлів оперативним персоналом котелень