Papers by Keyword: Modulated Structures

Abstract: Lead hafnate single crystals were characterized using single crystal x-ray diffraction under simultaneous application of hydrostatic pressure and high temperatures. The information on the structure of two intermediate phases, situated between antiferroelectric and paraelectric phases in the pressure-temperature phase diagram, has been obtained. The lower-temperature intermediate phase is characterized by incommensurate displacive modulations in Pb sublattice. The higher-temperature intermediate phase is characterized by oxygen framework distortion, primarily in the form of anti-phase tilts of the oxygen octahedra, which is also present in the lower-temperature intermediate phase.

Abstract: The anisotropic Ising model with competing interactions is investigated in wide temperature range and |J₁/J| parameters by means of Monte-Carlo methods. Static critical exponents of the magnetization, susceptibility, heat capacity, and correlation radius are calculated in the neighborhood of Lifshitz point. According to obtained results a phase diagram is plotted, the coordinates of Lifshitz point are defined, and a character of multicritical behavior of the system is detected.

Abstract: We report on possible types of spatially modulated antiferromagnetic structures in the biaxial multiferroic and their stability depending on the ratio of the magnetic anisotropy and flexomagnetoelectric interaction parameters.

Abstract: Transmission electron microscopy studies of the Ni2MnGa alloy showed that in the diffraction patterns there exist two additional effect apart from the spots given by the parent L21 Heusler phase and the tetragonal no modulate martensite. The first effect was the presence of sharp extra spots, lying on a direction significantly deviated from the <110>* for [001]β zone axis. These spots are connected with modulation of the parent phase. The value of the deviation angle is about 11-12°. The detailed analysis showed that the direction of the propagation vector of modulation is <641> type direction. The second effect visible in the [001]β diffraction patterns is the presence of the arcs located between the 220 type parent phase spots.. The analysis of this objects suggests that some chemical modulation exists with the period of <550>β. In this case short range ordering plays the essential role.