Polarized light studies of the ferroelastic domains of K₃Fe₅F₁₅

Abstract

The orthorhombic ferroelastic domai ns of K 3 Fe 5 F 15 , with prototypic tetragonal tungsten bronze(TIB) structure and mixed valency 3Fe2+f2Fe3+, have been studied at R.T. in polarized light on single crystals grown by high temperature solution growth with subsequent quenching from 973K. The birefringent ferroelastic domains exhibit a remarkable linear dichroism. The principal refractive indices and the principal extinction coefficients have been measured along the crystallographic axes, identified by means of x-ray measurements on a s ingle domain. The correlation between the refractive indices, the extinction coefficients and the cell parameters bas been established. The change of orientation of the vibration ellipse of the transmitted light due to dichroism has been observed.

Studies of single crystalline tetragonal tungsten bronze type K3Fe5F15, a potential magnetoelectric material

“…According to the optical studies of the orthorhombic ferroelastic domains at 298 K, 6 summarized in Figure 1, the orthorhombic domain patterns of the platelet served for optical studies are shown in Figures 2 (a)-(c) and are schematically represented in Figure 2 (d) .…”

“…4 We have synthesized stoichiometric single crystals of KFEF by high temperature solution growth with subsequent quenching from 973 K, according to the condition which was deduced from thermal analysis an_ d X-ray diffraction measurements. 5 After having established in a previous work the correlation between the refractive indices, extinction coefficients and the crystallographic axes at room temperature, 6 we have undertaken in the present work optical and magnetic measurements on single crystals of KFEF at l.ow temperatures with a view to clarifying the phase sequence of KFEF and exploring potential magnetoelectric properties.…”