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

Mesoscopic theory of defect ordering-disordering transitions in thin oxide films

Ordering of mobile defects in functional materials can give rise to fundamentally new phases possessing ferroic and multiferroic functionalities. Here we develop the Landau theory for strain induced ordering of defects (e.g. oxygen vacancies) in thin oxide films, considering both the ordering and wavelength of possible instabilities. Using derived analytical expressions for the energies of various defect-ordered states, we calculated and analyzed phase diagrams dependence on the film-substrate mismatch strain, concentration of defects, and Vegard coefficients. Obtained results open possibilities to create and control superstructures of ordered defects in thin oxide films by selecting the appropriate substrate and defect concentration.Comment: 30 pages, 5 figures, 1 appendi

Typology and Factorial Conditioning of Suicidal Behavior of Adolescents

The problem of suicidal behavior of an individual continues to remain relevant, due to the increase in the number of suicides among people of different ages, on the one hand, and insufficient information about the factors of suicidal behavior of an individual. The purpose of the study is to identify the factors that determine the formation of a certain type of personality who committed suicidal attempts in adolescence. In order to identify the types of adolescent suicides, there was conducted a survey of 20 doctors in psychiatric clinical hospitals in Moscow. The survey results were processed using cluster analysis. To identify the factorial conditioning of suicidal behavior of each personality type, a complex of psychodiagnostic techniques was used, focused on the study of the characteristics of the emotional, value-semantic and behavioral spheres of the personality. The obtained empirical data were processed with the help of factor analysis. Three clusters have been identified that combine similar personality characteristics of suicides. It was specified that among adolescents there are the following personality types: “militant” (22%), “sacrifice” (54%) and “self-deprecating” (24%). Each type of adolescent suicide is due to the characteristics of the emotional, value-semantic and behavioral spheres of their personality. To develop targeted programs for the prevention of suicidal behavior among adolescents, it is necessary to take into account the results of the study, since such programs should be aimed at blocking the factors that form a certain type of suicide

Typology and Factorial Conditioning of Suicidal Behavior of Adolescents

The problem of suicidal behavior of an individual continues to remain relevant, due to the increase in the number of suicides among people of different ages, on the one hand, and insufficient information about the factors of suicidal behavior of an individual. The purpose of the study is to identify the factors that determine the formation of a certain type of personality who committed suicidal attempts in adolescence. In order to identify the types of adolescent suicides, there was conducted a survey of 20 doctors in psychiatric clinical hospitals in Moscow. The survey results were processed using cluster analysis. To identify the factorial conditioning of suicidal behavior of each personality type, a complex of psychodiagnostic techniques was used, focused on the study of the characteristics of the emotional, value-semantic and behavioral spheres of the personality. The obtained empirical data were processed with the help of factor analysis. Three clusters have been identified that combine similar personality characteristics of suicides. It was specified that among adolescents there are the following personality types: “militant” (22%), “sacrifice” (54%) and “self-deprecating” (24%). Each type of adolescent suicide is due to the characteristics of the emotional, value-semantic and behavioral spheres of their personality. To develop targeted programs for the prevention of suicidal behavior among adolescents, it is necessary to take into account the results of the study, since such programs should be aimed at blocking the factors that form a certain type of suicide

Typology and Factorial Conditioning of Suicidal Behavior of Adolescents

The problem of suicidal behavior of an individual continues to remain relevant, due to the increase in the number of suicides among people of different ages, on the one hand, and insufficient information about the factors of suicidal behavior of an individual. The purpose of the study is to identify the factors that determine the formation of a certain type of personality who committed suicidal attempts in adolescence. In order to identify the types of adolescent suicides, there was conducted a survey of 20 doctors in psychiatric clinical hospitals in Moscow. The survey results were processed using cluster analysis. To identify the factorial conditioning of suicidal behavior of each personality type, a complex of psychodiagnostic techniques was used, focused on the study of the characteristics of the emotional, value-semantic and behavioral spheres of the personality. The obtained empirical data were processed with the help of factor analysis. Three clusters have been identified that combine similar personality characteristics of suicides. It was specified that among adolescents there are the following personality types: “militant” (22%), “sacrifice” (54%) and “self-deprecating” (24%). Each type of adolescent suicide is due to the characteristics of the emotional, value-semantic and behavioral spheres of their personality. To develop targeted programs for the prevention of suicidal behavior among adolescents, it is necessary to take into account the results of the study, since such programs should be aimed at blocking the factors that form a certain type of suicide

The role of the Fe/Mo cations ordering degree and oxygen non-stoichiometry on the formation of the crystalline and magnetic structure of Sr2FeMoO6‒δ

Single-phase Sr2FeMoO6-δ powders with various oxygen indices (δ) and degrees of the superstructural ordering (P) of the Fe/Mo cations were obtained from SrFeO2.52 and SrMoO4 reagents via solid-state synthesis. It has been established by means of the x-ray and neutron diffraction that, upon reducing the oxygen content and enhancing the superstructural ordering, the lengths of the Fe–O1 and Mo–O2 bonds in the crystal lattice increase, whereas the Fe–O2 and Mo–O1 bond lengths decrease. At the same time, the volume of the unit cell is reduced, which indicates an enhancement of the covalency degree of the bonds and stimulates a redistribution of the electron density, as well as an increase of the concentration of the spin-down charge carriers located in the conduction band on the Mo(t2g)↓ orbitals. This circumstance leads to an increase of the density of states at the Fermi level, accompanied by an amplification of the exchange interaction and elevation of the Curie temperature, which points to the leading role of the spin-polarized charge carriers at the Fermi level in the exchange interaction.publishe

Intermediate structural state in Bi1−xPrxFeO3 ceramics at the rhombohedral–orthorhombic phase boundary

Crystal structure of the Bi1−xPrxFeO3 ceramics of the compositions corresponding to the threshold concentrations separating the polar rhombohedral (R3c) and anti-polar orthorhombic (Pbam) phases has been investigated with X-ray diffraction, transmission electron microscopy and differential scanning calorimetry measurements performed in a broad temperature range. The structural study specifies the peculiarities of the temperature-driven transition into the non-polar orthorhombic (Pnma) phase depending on the structural state of the compounds at room temperature. The crystal structure analysis reveals the revival of the anti-polar orthorhombic phase upon the temperature-induced transition, thus assuming that it can be considered as the bridge phase between the polar rhombohedral and the non-polar orthorhombic phases.publishe