Anomalous behavior of dielectric response of quantum paraelectric CaTiO3 with iron impurities
E. A. Popova+*, E. A. Rumyantseva+, B. Kh. Khananov+, V. G. Zalessky+, S. V. Krivovichev*, S. G. Lushnikov+*
+Ioffe Institute, 194021 St. Petersburg, Russia
*Department of Crystallography, St. Petersburg State University, 199034 St. Petersburg, Russia
Abstract
Herein we report on the studies of lattice dynamics and crystal
structure of natural perovskite with the general
formula CaTiO3:0.01Fe by dielectric spectroscopy and X-ray diffraction
in a wide temperature range. In contrast to
the "chemically pure" synthetic perovskite, the lattice dynamics of
the Fe-containing natural sample exhibits a
structural instability in the vicinity of 240 K. Our studies of the
behavior of magnetic moment of CaTiO3:0.01Fe
demonstrate that in the temperature region from 4.3 to 300 K this
material is paramagnetic. No changes in the
crystal symmetry have been observed in the structural studies,
which can be explained by the small degree of lattice
distortions, as has been observed previously for isotopically
substituted SrTiO318. Conductivity measurements and
analysis of the dielectric response dispersion of CaTiO3:0.01Fe
have shown that the dispersion is due to the
Maxwell-Wagner mechanism and can be attributed
to oxygen vacancies present in the mineral.