Berlin 2012 – scientific programme
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MA: Fachverband Magnetismus
MA 33: Magnetic Coupling Phenomena/ Exchange Bias
MA 33.7: Talk
Wednesday, March 28, 2012, 17:00–17:15, EB 202
Magnetic exchange interactions in perovskites ATcO3 (A = Ca, Sr, Ba) with high Neel temperature studied from first principles — •Vladislav Borisov1, Igor Maznichenko2, Sergey Ostanin1, Arthur Ernst1, and Ingrid Mertig1,2 — 1Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle, Germany — 2Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, D-06099 Halle, Germany
An extraordinary high Neel temperature (TN) has been found for the 4d transition metal oxides ATcO3 (A = Ca, Sr, Ba) with the perovskite structure. The magnetic properties and the exchange interactions in the system were studied from first principles using the KKR-CPA method based on the multiple-scattering theory. For each perovskite, the most preferable magnetic configuration was found to be G-type antiferromagnetic with antiparallel alignment of the neighboring magnetic moments. The observed magnetic ordering is accounted for by the strong superexchange interaction between the Tc cations which is mediated by a pronounced overlap of the technetium 4d orbitals and oxygen p orbitals. We obtained the values of the Neel temperature TN of 840 K for CaTcO3 and 930 K for SrTcO3 which are in a good agreement with the recent experiments. For BaTcO3 which is not available so far, we predict the fundamental band gap of 0.3 eV and TN ≈ 1000 K. In general, an increase in the volume leads to a noticeable enhancement of TN whereas the presence of vacancies on both the oxygen and Tc sites significantly lowers the critical temperature as well as the magnetic moments of Tc cations.