Structure genesis and magnetic orderings in compounds of the ThCr2Si2 type

Abstract

It is shown in a phenomenological approach that the symmetry space group I4/mmm of the paramagnetic phase in compounds of the ThCr2Si2 type arises as a result of a structural phase transition from a close-packed paraphase with space group Im3m. It is found that the real magnetic orderings in compounds of the ThCr2Si2 type is described by transition parameters belonging to a single direction, along the line joining the points of maximum symmetry in the Brillouin zone of the I4/mmm group. It is shown that the variations of the modulus of the wave vector are a consequence of a change in the dopant concentration. The spatial dependence of the order parameter in the incommensurate phases is obtained for the corresponding universality classes.

Improvement of Ferroelectric Properties in Mo-Substituted Bi3.35La0.75Ti3O12 Films by Optimization of Heating Rate

“…There have been several theoretical attempts to explain the magnetic phase diagram of the A(M 1−x M x ) 2 Ge 2 compounds. In [6], a phenomenological theory of magnetic phase transitions in such compounds, considering heterogeneities of the structure due to the presence of the doping element, was developed. It explains the change in the magnetic structure by a decrease in the unit-cell volume due to the substitution of Fe atoms for Pd ones.…”

Structural study of U(Pd1 xFex)2Ge2at high pressure

“…The observed changes of the magnetic structure of U(Pd 1−x Fe x )Ge 2 caused by Fe substitution of Pd atoms at ambient pressure could not be explained in terms of the 'f-d hybridization model' by the modification of hybridization matrix elements, since their values V df ∝ 1/d 6 U−M and the U-M distance vary only very slightly for the Fe doping level studied, x < 0.03.…”

Features of incommensurate phases in multiferroics

“…Here α = α 0 (T -T c ), where T is the temperature and n is a degree of anisotropy. We discuss crystal structures that possess heterogeneity as a consequence of the fact that they are formed by various atoms [3]. Due to this, these structures have averaged space group symmetry.…”

“…3 The effect of fractal distribution of defects on incommensurate structure From the structure genesis point of view, the crystals structure formed by different atoms can be regarded as a derivative of the close packages structure [3]. Usually, the symmetry of real derivative structures is lower than that of degenerate close packed crystals constructed from similar spheres.…”

“…In doped crystals it is proper inhomogeneity of structure [3]. Presence of inhomogeneities, internal fields and impurities in structure leads to necessity to investigate influence of defects on incommensurable phases.…”