title: Orbitally induced hierarchy of exchange interactions in the zigzag antiferromagnetic state of honeycomb silver delafossite Ag3Co2SbO6.
abstract: We report the revised crystal structure, static and dynamic magnetic properties of quasi-two dimensional honeycomb-lattice silver delafossite Ag3Co2SbO6. The magnetic susceptibility and specific heat data are consistent with the onset of antiferromagnetic long range order at low temperatures with Néel temperature TN ∼ 21.2 K. In addition, the magnetization curves revealed a field-induced (spin-flop type) transition below TN in moderate magnetic fields. The GGA+U calculations show the importance of the orbital degrees of freedom, which maintain a hierarchy of exchange interaction in the system. The strongest antiferromagnetic exchange coupling was found in the shortest Co-Co pairs and is due to direct and superexchange interaction between the half-filled xz + yz orbitals pointing directly to each other. The other four out of six nearest neighbor exchanges within the cobalt hexagon are suppressed, since for these bonds the active half-filled orbitals turned out to be parallel and do not overlap. The electron spin resonance (ESR) spectra reveal a broad absorption line attributed to the Co(2+) ion in an octahedral coordination with an average effective g-factor g = 2.40 ± 0.05 at room temperature and show strong divergence of the ESR parameters below ∼150 K, which implies an extended region of short-range correlations. Based on the results of magnetic and thermodynamic studies in applied fields, we propose a magnetic phase diagram for the new honeycomb-lattice delafossite.
authors.affiliation: Faculty of Physics, Moscow State University, 119991 Moscow, Russia. zvereva@mig.phys.msu.ru.
authors.forename: E A
authors.initials: EA
authors.lastname: Zvereva
authors.affiliation: Faculty of Physics, Moscow State University, 119991 Moscow, Russia. zvereva@mig.phys.msu.ru.
authors.forename: M I
authors.initials: MI
authors.lastname: Stratan
authors.affiliation: Institute of Metal Physics, S. Kovalevskoy St. 18, 620990 Ekaterinburg, Russia.
authors.forename: A V
authors.initials: AV
authors.lastname: Ushakov
authors.affiliation: Chemistry Faculty, Southern Federal University, 344090 Rostov-on-Don, Russia.
authors.forename: V B
authors.initials: VB
authors.lastname: Nalbandyan
authors.affiliation: Chemistry Faculty, Southern Federal University, 344090 Rostov-on-Don, Russia.
authors.forename: I L
authors.initials: IL
authors.lastname: Shukaev
authors.affiliation: Département de Physique, Université de Liége, B-4000 Sart Tilman, Belgium.
authors.forename: A V
authors.initials: AV
authors.lastname: Silhanek
authors.affiliation: Institute of Physics, Goethe University Frankfurt, 60438 Frankfurt/M, Germany and Faculty of Science, Physics Department, Fayoum University, 63514 Fayoum, Egypt and Center for High Pressure Science & Technology Advanced Research, 1690 Cailun Rd, Shanghai, 201203, P.R. China.
authors.forename: M
authors.initials: M
authors.lastname: Abdel-Hafiez
authors.affiliation: Institute of Metal Physics, S. Kovalevskoy St. 18, 620990 Ekaterinburg, Russia and Ural Federal University, 620002 Ekaterinburg, Russia.
authors.forename: S V
authors.initials: SV
authors.lastname: Streltsov
authors.affiliation: Faculty of Physics, Moscow State University, 119991 Moscow, Russia. zvereva@mig.phys.msu.ru and Ural Federal University, 620002 Ekaterinburg, Russia and National University of Science and Technology "MISiS", 119049 Moscow, Russia.
authors.forename: A N
authors.initials: AN
authors.lastname: Vasiliev