TY - JOUR
T1 - Cooperative behavior of Zn cations in Bi-based perovskites
T2 - A comparison of (Bi,Sr)2ZnNbO6 and (Bi,Sr)2MgNbO6
AU - Takagi, Shigeyuki
AU - Cooper, Valentino R.
AU - Singh, David J.
PY - 2011/3/21
Y1 - 2011/3/21
N2 - We investigated the polar behavior of the double perovskite (Bi,Sr) 2MgNbO6 using first-principles density-functional theory calculations. We find that the magnitude (75 μC/cm2) and direction (along [111]) of the polarization are comparable to our previous results for the A-site size difference (Bi,Sr)2ZnNbO6 and (Bi,Pb) 2ZnNbO6 systems. However, comparisons with the (Bi,Sr)2ZnNbO6 compound indicate that the presence of Zn modestly enhances the off-centering of the Sr and Nb cations as well as the Born effective charges of both Bi and Nb. Analogous to the corresponding Pb-based perovskites, Pb(Mg1/3Nb2/3)O3 and Pb(Zn 1/3Nb2/3)O3, we demonstrate that the differences in the experimentally observed critical temperatures are related to the differences in polarization between the two materials. A local dipole analysis indicates that the most significant contribution arises from the enhanced cooperative couplings with the larger Zn displacements.
AB - We investigated the polar behavior of the double perovskite (Bi,Sr) 2MgNbO6 using first-principles density-functional theory calculations. We find that the magnitude (75 μC/cm2) and direction (along [111]) of the polarization are comparable to our previous results for the A-site size difference (Bi,Sr)2ZnNbO6 and (Bi,Pb) 2ZnNbO6 systems. However, comparisons with the (Bi,Sr)2ZnNbO6 compound indicate that the presence of Zn modestly enhances the off-centering of the Sr and Nb cations as well as the Born effective charges of both Bi and Nb. Analogous to the corresponding Pb-based perovskites, Pb(Mg1/3Nb2/3)O3 and Pb(Zn 1/3Nb2/3)O3, we demonstrate that the differences in the experimentally observed critical temperatures are related to the differences in polarization between the two materials. A local dipole analysis indicates that the most significant contribution arises from the enhanced cooperative couplings with the larger Zn displacements.
UR - http://www.scopus.com/inward/record.url?scp=79961046339&partnerID=8YFLogxK
U2 - 10.1103/PhysRevB.83.115130
DO - 10.1103/PhysRevB.83.115130
M3 - Article
AN - SCOPUS:79961046339
SN - 1098-0121
VL - 83
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 11
M1 - 115130
ER -