Title: First-principles study of the magnetic interactions in honeycomb $\mathrm{N}{\mathrm{a}}_2\mathrm{Ir}{\mathrm{O}}_3$

Abstract

Honeycomb iridate Na2IrO3, a Jeff=1/2 magnet, is a potential platform for realizing quantum spin liquid. Many experiments have shown that its magnetic ground state is a zigzag antiferromagnetic order. However, there is still a lack of consensus on the theoretical model explaining such order, since its second-nearest-neighbor (NN) and long-range third-NN magnetic interactions are highly unclear. By properly considering the orbital moments achieved through constraining their directions in first-principles calculations, we obtain that the relative angle between orbital and spin moments is fairly small and in the order of several degrees, which thus validates the Jeff=1/2 state in Na2IrO3. Surprisingly, we find that the long-range third-NN Heisenberg interactions are sizable, whereas the second-NN magnetic interactions are negligible. Furthermore, we show that sizable long-range third-NN Heisenberg interactions closely correlate with the appreciable distribution of Wannier orbitals of Jeff=1/2 states over the three NN Ir atoms. Based on our study, we propose a minimal J1-K1-G1-J3 model in which the magnetic excitations have an intensity peak at 5.6 meV, consistent with the inelastic neutron-scattering experiment [Phys. Rev. Lett. 108, 127204 (2012)10.1103/PhysRevLett.108.127204]. The present work demonstrates again that constraining orbital moments in first-principles calculations is a powerful way to investigate the intriguing magnetism inmore » Jeff=1/2 magnets, and it paves the way toward gaining a deep insight into the novel magnetism discovered in the honeycomb Jeff=1/2 magnets« less

Authors:

Hou, Y. S.; Yang, J. H.; Xiang, H. J.; Gong, X. G.

Publication Date:

2018-09-01

Research Org.:

National Renewable Energy Lab. (NREL), Golden, CO (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE)

OSTI Identifier:

1475530

Report Number(s):

NREL/JA-5K00-72528
Journal ID: ISSN 2469-9950; PRBMDO

DOE Contract Number:  

AC36-08GO28308

Resource Type:

Journal Article

Journal Name:

Physical Review B

Additional Journal Information:

Journal Volume: 98; Journal Issue: 9; Journal ID: ISSN 2469-9950

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; magnetism; iridates; density functional theory