Magnetic diffuse scattering from Zn-Mg-RE and Cd-Mg-RE (RE: rare-earth) icosahedral quasicrystals

Abstract

Ferroelectricity is directly coupled with the ordering of crystal structure.For discontinuous transitions the X-ray diffuse scattering (XDS) in the low and high temperature phase can be expected quite different.In the continuous transition; the transformation is due to progressive and cooperative disordering.In the ferroelectric structures containing polar groups the increasing temperature produces a disordering of these groups.Above transition point the structure becomes centrosymmetric in the macroscopic scale but still contains small polar nanodomains.Our recent results obtained by the recording of XDS using the X-ray diffractometer with the CCD detector will be presented.In the quantum paraelectric crystals in the centrosymmetric para-phase the XDS is associated with ferroelectric polar nanoregions.In the relaxor materials with diffuse transformations the polar nanoregions in the para-phase have been found.The XDS study of the structural arrangement and glass-like transition behavior of relaxor Pb(B'0.5B'0.5)O3where B'=Nb; Ta shows the occurrence of the freezing antiferro-and ferro-electric fluctuations and the small nano-regions with ordered B'/B' cations.Although the sodium nitrate (NaNO2) crystal is typical order-disorder ferroelectrics with the simple structure; the arrangement of atoms in the nanodomains in the para-phase in the para-phase associated with the modulation wave and with the polar nano-region was found.The results of XDS studies of ferroelectric SbSI crystals with the pseudo Jahn-Teller transition and the semiconducting and weak ferroelectric Sb2S3 crystals will be presented.