MAGNETORESISTANCE AND HALL EFFECT CAUSED BY BERRY CURVATURE IN Sr ₂FeMoO₆- DOUBLE PEROVSKITE

The paper focuses on transport properties of double perovskite Sr 2FeMoO6-(delta), which were studied experimentally and using first principles calculations. The strontium ferromolybdate specimens were prepared using citrate-gel method followed by compacting and thermal treatment at different regimes. The Hall effect was calculated using Quantum Espresso and Wannier90 software packages. The study confirmed high sensitivity of Sr2FeMoO6 to the processing parameters such as pressure and temperature of powder compacting as well as the temperature and duration of the subsequent annealing in Ar/O (2) atmosphere. The optimal regime of compacting to avoid cracking involved pressing under 4 GPa at T = 800 K. Further heat treatment of the compacted specimens in Ar/O (2) atmosphere has shown that three types of electric conductivity, namely metallic, semiconducting and mixed one can be realized in the Sr (2) FeMoO6 specimens. The highest magnitude of magnetoresistance was found in the semiconducting specimen (about 44%), while the specimen of metallic type demonstrated magnetoresistance of about 21%. The elevated values of magnetoresistance in the semiconducting specimen were achieved due to conduction mechanism related to tunneling through intergrain dielectric layers formed by secondary SrMoO (4) phase. The Hall effect was computed by constructing the Hamiltonian in the maximally-localizedWannier functions basis. Calculations of the Berry curvature, which is the origin of the high intrinsic Hall effect showed that its highest magnitudes concentrate near avoided band crossings gapped out due to spin-orbit coupling. The Hall conductivity calculated by integrating the Berry curvature over all occupied bands was found to be similar to 22 S/cm.