Long-wavelength phonons and effective charges in complex perovskite compounds Ba(Mn1/3Ta2/3)O3 and Ba(Ni1/3Ta2/3)O3

Effect of La/K A‐site Substitutions on the Ordering of Ba(Zn1/3Ta2/3)O3

“…x ‫ס‬ 0.2, 0.02, and 0.0. Lines at 375 and 424 cm −1 , which are attributed to the torsional-mode vibrations of the B-site ions, [16][17][18] are broadened and shifted when x ‫ס‬ 0.02 for the BLZT ceramic, whose long-range ordering is almost zero. When the value of x of the BLZT ceramic increases to 0.2, the peak at 424 cm −1 originally shifts to 414 cm −1 and sharpens again.…”

Study of crystal-field excitations and infrared active phonons in TbMnO3

“…The Born effective charges Z * reflect local dipole moment and play a crucial role in understanding the physics of the ferroelectric and the piezoelectric materials. Its variation influences the magnitude of the frequency splitting of the LO and the TO phonons as follows [41]: j is the phonon mode and k is the atom with mass m k in the unit cell of volume ν c . With the electric neutrality of the system and considering that the Z * Tb = Z * Mn [25,42], we calculate the variation of the effective charges δZ * O and δZ * R/Mn induced by a magnetic field:…”

Micro-Raman and infrared studies of multiferroic TbMn2O5

“…Within this formalism, Vermette et al [8] have reproduced the macroscopic electric polarization of HoMnO 3 , at low temperature, with no adjustable parameters. The sum of the Born effective charge Z * k is connected to the frequencies of the TO and LO modes as follows [28]: ) and considering an average valence state of Mn ions (Z * Mn ) [29,30], we obtain: . The variation of the effective charges of oxygen (δ Z * O ), induced by a magnetic field, is determined according to the following equation:…”