Проект направлен на комплексное экс

Проект направлен на комплексное экспериментальное и теоретическое исследование магнитокалорических свойств перспективных материалов для технологии магнитного охлаждения в переменных магнитных полях. В рамках данного проекта под комплексным исследованием магнитокалорических свойств понимается исследование магнитных, тепловых и структурных характеристик материалов, связанных (или влияющих) с их магнитокалорическими свойствами.

Целью исследований, планируемых проводить в предлагаемом проекте, являются:
1. Установление основных особенностей магнитокалорического эффекта в переменных магнитных полях в различных магнитных материалах;
2. Установление природы гигантского магнитокалорического эффекта (ГМКЭ) в материалах с магнитоструктурными фазовыми переходами и определение вкладов различных механизмов в общий магнитокалорический эффект. Решение этой задачи имеет важное значение, так как позволяет определить пути поиска новых перспективных магнитокалорических материалов;
3. Установление температурных, полевых и частотных интервалов наблюдения обратимого МКЭ в переменных магнитных полях в различных магнитокалорических материалах;
4. Исследование кинетики релаксационных явлений в магнитных материалах и их связи с магнитными и магнитокалорическими свойствами, установление характерных времен релаксации магнитной и решеточной подсистем;
5. Изучение влияния долговременного действия переменного магнитного поля на магнитные и магнитокалорические свойства материалов с целью установления природы возможного деградирующего действия переменного поля на магнитные и структурные свойства;
6. Установление класса наиболее перспективных магнитокалорических материалов с точки зрения их поведения в переменных магнитных полях (гигантский МКЭ, широкая температурная область наблюдения МКЭ вблизи комнатных температур, физическая и механическая прочность, и т.д.).

Актуальность проекта обусловлена практическими потребностями. В настоящее время практически все исследования магнитокалорических свойств проводились и проводятся при постоянных полях (косвенные методы оценки МКЭ) или при разовых циклах изменения поля. Между тем, в холодильных машинах рабочее тело будет подвергаться периодическому действию магнитного поля. Магнитокалорические свойства материалов в переменных и постоянных магнитных полях могут существенно отличаться, а долговременное воздействие переменного поля даже может привести к существенному ухудшению их свойств. Механизмов, приводящих к таким различиям, может быть несколько, и в разных материалах это может проявляться по разному. По существу, влияние этих механизмов на магнитокалорические свойства материалов, на их физическую, магнитную, механическую прочности, к настоящему времени не исследовано ни экспериментально, ни теоретически. На наш взгляд, наиболее существенными являются следующие механизмы: релаксационные явления при магнитных и структурных фазовых переходах; релаксация спин-фононного взаимодействия; необратимый характер индуцированных магнитным полем фазовых переходов 1 рода. Последний может проявиться даже при малых частотах изменения поля. Температурные гистерезисы, свойственные переходам 1 рода, могут привести к тому, что в определенных температурных областях индуцированные внешним магнитным полем фазовые переходы будут иметь необратимый характер. Величины магнитокалорического эффекта при первом и последующих циклах включения поля в этих материалах будут существенно отличаться. В то же время, материалы с магнитоструктурными фазовыми переходами, известные как материалы с гигантскими МКЭ, рассматриваются как одни из наиболее перспективных в технологии магнитного охлаждения. К этим же материалам можно отнести и материалы, в которых в обычном смысле не происходит структурного перехода с изменением симметрии решетки, но наблюдается резкое изменение параметров решетки. В этих материалах, в дополнение к изменению магнитной энтропии, происходит изменение энтропии решетки вследствие сильной магнитострикции. Суммарное изменение энтропии дает гигантскую величину МКЭ. При этом соотношение вкладов для большинства исследованных материалов не установлено.

Исследование магнитокалорического эффекта в переменных магнитных полях естественным образом приводит нас к исследованию кинетики фазовых переходов. Особый интерес представляют магнитоструктурные фазовые переходы. В последнее время большое внимание привлекают сплавы Гейслера с эффектом памяти формы, которые могут найти широкое практическое применение. В этих сплавах в области магнитоструктурных переходов наблюдается большая величина МКЭ. Исследование МКЭ, намагниченности, магнитострикции в переменных полях позволит изучать кинетику фазовых переходов в этих материалах, определить области их практического применения.

С фундаментальной точки зрения представляет интерес исследование влияния переменного магнитного поля на магнитные свойства материалов вблизи фазовых переходов. Особенности магнитных фазовых переходов, характер изменения магнитного взаимодействия, особенности спин-фононного взаимодействия, магнитострикция и другие параметры в переменных магнитных полях - эти вопросы теоретически и экспериментально будут решаться в данном проекте наряду с основной задачей.

Результаты (английский) 1:

The project aims at an integrated experimental and theoretical study on the magnitokaloričeskih properties of advanced materials for magnetic refrigeration technology in the variable magnetic fields. Under this project, a comprehensive study of the properties of magnitokaloričeskih refers to the study of magnetic, thermal and structural characteristics of the materials (or affecting) with their magnitokaloričeskimi properties.The aim of the research planned to carry out the proposed project are:1. determination of the main features of the magnitokaloričeskogo effect in a variable magnetic fields in various magnetic materials;2. establishing the nature of giant magnitokaloričeskogo effect (GMKÈ) in the magnitostrukturnymi phase transitions, and the definition of deposits of different mechanisms in common magnitokaloričeskij effect. The solution to this problem is important because it allows you to identify promising new search paths magnitokaloričeskih materials;3. setting temperature, field and frequency monitoring intervals reversible FEA in magnetic fields variables in different magnitokaloričeskih materials;4. Study of the kinetics of relaxation phenomena in magnetic materials and their relation with magnetic and magnitokaloričeskimi properties to establish the characteristic relaxation times of magnetic and lattice subsystems;5. to examine the effects of long-term actions of alternating magnetic field on magnetic and magnitokaloričeskie properties of materials with a view to establishing the nature of the possible actions of a degrading AC field on magnetic and structural properties;6. the establishment of the most promising class magnitokaloričeskih materials in terms of their behaviour in a variable magnetic fields (giant MEE, wide temperature range monitoring MEE near room temperature, physical and mechanical strength, etc.). Relevance the project is driven by practical needs. At present, almost all of the studies conducted and property magnitokaloričeskih are permanent fields (indirect methods of estimating MEE) or single loops, change fields. Meanwhile, in refrigerating machines working body will be subject to periodic action of a magnetic field. Magnitokaloričeskie properties of materials in variable and fixed magnetic fields may differ significantly, and the long-term impact of variable fields may even lead to a significant deterioration of their properties. Mechanisms leading to such differences, there can be several different materials and this can manifest itself in different ways. Essentially, the effect of these mechanisms on the magnitokaloričeskie properties of materials, their physical, magnetic, mechanical strength, so far not investigated nor experimentally nor theoretically. In our view, the most significant are the following mechanisms: relaxation phenomena in magnetic and structural phase transitions; relaxation of spin-Phonon interaction; the irreversible nature of the magnetic field-induced phase transitions 1 kind. The latter may occur even at low frequencies the field was changed. Temperature characteristic of gisterezisy 1 kind of conversions can result in certain temperature fields induced by external magnetic field phase transitions will be irreversible. Values of magnitokaloričeskogo effect in the first and subsequent cycles enable fields in these materials will differ significantly. At the same time, materials with magnitostrukturnymi phase transitions, known as materials with gigantic MEE, regarded as one of the most promising technology of the magnetic cooling. These same materials can be attributed and content that is not in the usual sense of the structural transition occurs with a change of symmetry of the lattice, but there has been a dramatic change in the parameters grid. In these materials, in addition to the change of magnetic entropy, the entropy change gratings as a consequence of the strong magnetostriction. The total change in entropy gives a huge amount of MEE. While the ratio of deposits for most of the materials studied. Study on the magnitokaloričeskogo effect of variable magnetic fields naturally leads us to study the kinetics of phase transitions. Of particular interest are the magnitostrukturnye phase transitions. Lately, great attention is paid to the alloys Geissler with shape memory effect that may find widespread application. In these alloys in the area there are large navigation magnetostructural value MEE. Study on the FINITE ELEMENT METHOD, magnetization, magnetostriction in variable fields will allow to study the kinetics of phase transitions in these materials determine their practical application.From a fundamental point of view is interesting research into the influence of alternating magnetic field on magnetic properties of materials near the phase transitions. Features magnetic phase transitions, magnetic nature of the changes, especially the interaction of spin-Phonon interaction, magnetostriction and other parameters of the variable magnetic fields-these issues theoretically and experimentally will be addressed in this project along with the main task.

Результаты (английский) 2:

The project aims at a comprehensive experimental and theoretical study of magnetocaloric properties of advanced materials for magnetic refrigeration technology in alternating magnetic fields. The project under the comprehensive study of magnetocaloric properties is understood a study of magnetic, thermal and structural properties of materials related (or affect) their magnetocaloric properties. The aim of research, planned to carry out the proposed project are: 1. Establishment of the basic features of the magnetocaloric effect in alternating magnetic fields in a variety of magnetic materials; 2. Establishing the nature of a giant magnetocaloric effect (GMKE) in materials with magnetostructural phase transitions and determine the contribution of various mechanisms in the overall magnetocaloric effect. This task is important because it allows to determine the path to search for new promising magnetocaloric materials; 3. Determination of temperature, field and frequency intervals surveillance reversible FEM in alternating magnetic fields in different magnetocaloric materials; 4. Investigation of the kinetics of relaxation phenomena in magnetic materials and their relation to magnetic and magnetocaloric properties, setting the characteristic relaxation time of the magnetic and lattice subsystems; 5. The study of the effect of long-term action of the alternating magnetic field on the magnetic and magnetocaloric properties of materials in order to establish the nature of a possible degrading action of the alternating field on the magnetic and structural properties; 6. Establishing the most promising class of magnetocaloric materials in terms of their behavior in alternating magnetic fields (FEM giant, wide temperature range surveillance FEM near room temperature, physical and mechanical strength, etc.). The relevance of the project due to the practical needs. At present, almost all of the studies were conducted, and magnetocaloric properties are held in constant fields (indirect methods of estimation FEM) or single cycles of change in the field. Meanwhile, in the refrigeration working medium will be subject to periodic action of a magnetic field. Magnetocaloric properties of materials in variable and fixed magnetic fields may differ materially, and the long-term effects of the alternating field may even lead to a significant deterioration of their properties. Mechanisms that lead to such differences may be several different materials and it can manifest itself in different ways. Essentially, the effect of these mechanisms on the magnetocaloric properties of the materials, their physical, magnetic, mechanical strength, to date, has not been investigated either experimentally or theoretically. In our opinion, the most important are the following mechanisms: relaxation phenomena in magnetic and structural phase transitions; relaxation of the spin-phonon interaction; irreversible magnetic field induced phase transitions of one kind. The latter can occur even at low frequencies the field changes. Thermal hysteresis inherent in transitions 1 kind may lead to the fact that in certain areas the temperature induced by an external magnetic field, phase transitions will be irreversible. The values ​​of the magnetocaloric effect in the first and subsequent cycles of the inclusion of the field in these materials will vary greatly. At the same time, materials magnetostructural phase transitions, known as materials with giant MCE, considered as one of the most promising technologies in magnetic cooling. These same materials can be attributed to materials that are not in the usual sense of the structural transition occurs with a change in the lattice symmetry, but a sharp change in the lattice parameters. In these materials, in addition to the change of the magnetic entropy change of the entropy of the lattice occurs due to the strong magnetostriction. The total entropy change provides tremendous value FEM. The ratio of deposits for most of the investigated material is not established. The study of the magnetocaloric effect in alternating magnetic fields naturally leads us to the study of the kinetics of phase transitions. Of particular interest are magnetostructural phase transitions. Recently, much attention is paid to the Heusler alloys with shape memory effect, which can find wide practical application. In these alloys in magnetostructural transitions observed large quantity of FEM. The research FEM, magnetization, magnetostriction in alternating fields will allow to study the kinetics of phase transitions in these materials, to identify areas of their practical application. From a fundamental point of view of interest to study the influence of an alternating magnetic field on the magnetic properties of materials near phase transition. Features magnetic phase transitions, changes in the nature of magnetic interactions, especially the spin-phonon interaction, magnetostriction, and other parameters in alternating magnetic fields - these questions theoretically and experimentally will be addressed in this project in addition to the main task.

Результаты (английский) 3:

the project integrated experimental and theoretical study магнитокалорических properties of advanced materials for magnetic refrigeration technology in the variable magnetic fields.the project under the comprehensive study магнитокалорических properties is defined as the study of the magnetic, thermal and structural properties of materialsassociated (or impact) with their магнитокалорическими properties.

to research planned to hold in the proposed project are:
1.the main characteristics of the магнитокалорического effect variable magnetic fields of different magnetic materials;
2.the nature of the магнитокалорического effect (гмкэ) in materials with магнитоструктурными фазовыми gradients and the contributions of various mechanisms in the магнитокалорический effect.this task is important, as it allows to identify ways to search for promising new магнитокалорических materials;
3. setting temperature.field and frequency intervals of observation обратимого fea in the variable magnetic fields in different магнитокалорических materials;
4.study on the kinetics of relaxation phenomena in magnetic materials and their connection with the magnetic and магнитокалорическими properties, the characteristic relaxation times, magnetic and решеточной subsystems;
5.study on the impact of long-term operation of ac magnetic field on the magnetic properties and магнитокалорические materials to determine the nature of the possible деградирующего alternating field atand structural properties.
6. the class of the most prospective магнитокалорических materials in terms of their behaviour in the variable magnetic fields (giant fea...the temperature field fea near room temperature monitoring, physical and mechanical strength, etc.).

the project due to the practical needs.currently, almost all studies магнитокалорических properties were conducted at constant fields (indirect estimation methods of fea) or in the different cycles of the fields. meanwhile, thein refrigerating machines working body will be subject to periodic action of magnetic field. магнитокалорические properties of materials in variable and fixed magnetic fields can vary significantly.a long-term effect of ac field may even lead to a substantial deterioration of their properties. the mechanisms leading to such differences, there may be several.in a variety of materials that may manifest itself in different ways. essentially, the impact of these mechanisms on the магнитокалорические properties of materials, their physical, magnetic, mechanical strengthto date, we have not examined either experimentally or theoretically. in our view, the most important are the following mechanisms: our phenomenon in the magnetic and structural phase crossings;relaxation spin фононного interaction; irreversible phase transitions induced by the magnetic field of 1 kind. the latter may occur even at low frequencies of the fields. temperature гистерезисы,in passages 1 kind can lead to the fact that in certain temperature fields induced pluripotent external magnetic field phase transitions will be irreversible.the магнитокалорического effect at the first and subsequent rounds of the field in these materials will be significantly different. at the same time, materials with магнитоструктурными фазовыми gradients.materials with giant known as fea, regarded as one of the most promising technology of magnetic refrigeration. the same material can be classified as materialwhich in the usual sense is not a structural transition to change the symmetry of the lattice, but there has been a dramatic change in the lattice parameters. in these materials, in addition to the change of magnetic entropythere is a change of entropy lattice due to strong магнитострикции. cumulative change of entropy gives a value of fea.the ratio of deposits to the majority of the material has not been established.

study магнитокалорического effect variable magnetic fields naturally leads us to the study of kinetics of phase transitions.of particular interest is the магнитоструктурные phase transitions. recently, much attention has гейслера alloys with shape memory effect, which can find wide practical application.in these alloys in the field of магнитоструктурных crossings is the large size of the fea. study of fea, намагниченности,магнитострикции in variable fields will study the kinetics of phase transitions in these materials, to identify areas of their application.

from the fundamental point of view of interest was the study of the influence of ac magnetic field on the magnetic properties of the materials near phase transitions. characteristics of magnetic phase transitions.the nature of magnetic interactions, especially the spin фононного interactionmagnetostriction and other parameters in the variable magnetic fields - these questions theoretically and experimentally will be addressed in the draft, together with the main task.