Dresden 2011 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 44: Magnetic Half-metals and Oxides I
MA 44.5: Vortrag
Mittwoch, 16. März 2011, 18:00–18:15, HSZ 401
Structural distortions and the nature of metal-insulator transition in ferromagnetic hollandite K2Cr8O16 — •Alexey Ushakov1, Sergey Streltsov2, Toriwaki Toriyama3, Toshiki Konishi4, Yukinori Ohta3, Akiko Nakao5, Hironori Nakao5, Masahiko Isobe6, Yutaka Ueda6, and Daniil Khomskii1 — 1II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln, Germany — 2Institute of Metal Physics, S.Kovalevskoy St. 18, 620041 Ekaterinburg GSP-170, Russia — 3Department of Physics, Chiba University, Chiba 263-8522, Japan — 4Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522, Japan — 5Inst. Mat. Struct. Science, Photon Factory, Tsukuba, Ibaraki 305-0801, Japan — 6Materials Design and Characterization Laboratory, Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
It was recently discovered (K.Hasegawa et al. Phys.Rev.Lett.103, 146403 (2009)) that the ferromagnetic chromium hollandite K2Cr8O16 experiences metal-insulator transition (IMT) at TIMT=90 K, with the retention of ferromagnetism. The nature of this transition remained unclear. Detailed structural investigation demonstrated that there occurs at this transition a structural transition from the tetragonal I4/m to monoclinic P21/a phase, with the appearance of dimerization – inequivalent Cr-Cr distances, but without any charge ordering. By ab-initio band structure calculations, using different methods, we propose that IMT in K2Cr8O16 is caused by a Peierls-like dimerization in one-dimensional “columns” made of four coupled Cr chains.