Atomic Displacement Relationship to Curie Temperature and Spontaneous Polarization in Displacive Ferroelectrics

Polar octahedral rotations: A path to new multifunctional materials

“…Second, it is difficult to prove using first-principles calculations alone whether or not the polarization can be switched to a symmetry-equivalent state with an electric field small enough to be practically applied in a laboratory. Ca 3 Mn 2 O 7 does satisfy Abrahams' structural criteria for ferroelectricity [16] but the switching experiment itself may be challenging. Still, Ca 3 Mn 2 O 7 is a material where R 1 induces a linear magnetoelectric effect, R 2 induces weak ferromagnetism, and the combination of R 1 and R 2 induces ferroelectricity, all of which should lead to rich structural, (anti)ferromagnetic, and magnetoelectric domain configurations.…”

“…Additionally, when we speak of "ferroelectricity" we are referring to polar structures in which the polarization can in principle be switched to a symmetry-equivalent state with an applied electric field and that satisfy the simple structural criteria devised by Abrahams and co-workers. [16] 2. Octahedral Rotations and Ferroelectricity: Origin and Design…”

Defect structure dependence on composition in lithium niobate

“…It is notable that replacement of 9.6 atom% of the Li-site occupancy by Nb atoms, for a crystal composition of [Li0.9o4Nb0.o96]Nbo.92303, causes a reduction of over 120 K in Curie temperature. The Curie temperature may also be predicted, both in stoichiometric and in congruent lithium niobate, by means of the atomic displacement of the Nb atoms at room temperature from the midpoint between adjacent planes of O atoms normal to the polar axis, using the relationship of Abrahams, Kurtz & Jamieson (1968). The displacements of 0.2768 and 0.2701/~, respectively correspond to the predicted Tc = 1532 and 1459 K, compared with experimental values of 1471 and 1402 K. In view of the simplifications leading to the original relationship Tc = (2.00 + 0.09) x 104(Az) 2 K, both absolute magnitudes and the difference between predicted Curie temperatures are regarded as satisfactory.…”

Dielectric and thermal properties, expansion, and high-temperature plastic deformation of Cd4Na(VO4)3

“…Examination of the published atomic coordinates suggests that the crystal is ferroelectric (Abrahams & Keve, 1971) since all atoms are apparently displaced by small but significant distances from the positions required for the prototypic centrosymmetric space group Prima. The predicted Curie temperature, based on the displacement relationship of Abrahams, Kurtz & Jamieson (1968), lies in the range 320-450 K. Detection of a very small polarization in a preliminary piezoelectric investigation initially supported the possibility of ferroelectricity, as did the observation of an endotherm on heating and an exotherm on cooling at about 80 K below the melting point. More detailed study required larger high-quality crystals; this paper reports their growth and the results thereby found and illustrates the importance of correct space-group assignment.…”