A Polar Magnetic and Insulating Double Corundum Oxide: Mn<sub>2</sub>MnSbO<sub>6</sub> with Ordered Mn(II) and Mn(III) Ions
Hai L. Feng, Chang‐Jong Kang, Bongjae Kim, Kyoo Kim, Mark Croft, Sizhan Liu, Trevor A. Tyson, Eli Stavitski, Rui Zu, Venkatraman Gopalan, Saul H. Lapidus, Corey E. Frank, Youguo Shi, David Walker, M. Greenblatt
Abstract
A new magnetic insulator Mn2MnSbO6 with a polar crystal structure and an ordered Mn2+ and Mn3+ arrangement was synthesized under a high pressure of 7.5 GPa and 1300 °C. The crystal structure of Mn2MnSbO6, investigated by synchrotron powder X-ray diffraction, was found to be isomorphous with that of Ni3TeO6-type, space group R3. The non-centrosymmetric structure was confirmed by the second-harmonic generation measurements. The X-ray absorption near-edge spectroscopy measurement confirmed the nominal oxidation states of Mn2+2Mn3+SbO6. Magnetic measurements indicate that Mn2MnSbO6 orders antiferromagnetically below 44 K and undergoes a field-induced spin-flop transition at 5 K. First-principles calculations indicate an antiferromagnetic ground state with up/up/up/down/down/down (uuuddd) spin configuration of the six crystallographically unique Mn ions in the c-axis doubled magnetic structure. The density functional theory calculations also substantiate the experimentally observed charge ordering of the Mn2+/Mn3+ ions and the insulating behavior due to a bandgap of 0.52 eV. To the best of our knowledge, this is the first double corundum oxide containing Jahn–Teller active Mn3+ ions.