Magnetoelectric Interactions in Mn- and Co-Doped Incipient Ferroelectrics from Density Functional Calculations

Abstract

We study the interactions between Mn impurities substituting for different cations in the incipient ferroelectric perovskites SrTiO₃ and KTaO₃. Using the LSDA+ U, we show that magnetic interactions J between off-centered Mn ²⁺ _A ions substituting for Sr in SrTiO₃ and inducing ferroelectric instability in the system is negligible. For the nearest and next nearest neighbours |J_AA /k_B |<5 K. The calculations for KTaO₃ with Mn in K site show the stability of Mn in off-central positions shifted by 0.7 Å along the cubic axes. We have obtained that there is only one potential well for Mn_A located near a Mn_B in KTaO₃:Mn. It corresponds to Mn_A shift towards the Mn_B by 0.8 Å. We predict that Co substituting for Sr in SrTiO₃ should be stable in off-central positions shifted by 1.0 Å along a cubic axis.

Acknowledgments

The authors thank the PICS program (Contracts CNRS No. 4767, NASU No. 295), the MSMT CR (Project No. 1M06002) for financial support and the IFW Dresden (Germany) for using their computer facilities.