Unquenched $e_g^1$ orbital moment in the Mott insulating antiferromagnet KOsO4

Abstract

Applying the correlated electronic structure method based on density functional theory plus the Hubbard $U$ interaction, we have investigated the tetragonal scheelite structure Mott insulator KOsO${}_4$, whose $e_g^1$ configuration should be affected only slightly by spin-orbit couping (SOC). The method reproduces the observed antiferromagnetic Mott insulating state, populating the Os $d_{z^2}$ majority orbital. The quarter-filled $e_g$ manifold is characterized by a symmetry breaking due to the tetragonal structure, and the Os ion shows a crystal field splitting ${\Delta }_{cf}$ = 1.7 eV from the $t_{2g}$ complex, which is relatively small considering the high formal oxidation state Os${}^{7+}$. The small magnetocrystalline anisotropy before including correlation (i.e., in the metallic state) is increased by more than an order of magnitude in the Mott-insulating state, a result of a strong interplay between large SOC and a strong correlation. In contrast to conventional wisdom that the $e_g$ complex will not support orbital magnetism, we find that for the easy axis [100] direction the substantial Os orbital moment $M_L\approx -0.2{\mu }_B$ compensates half of the Os spin moment $M_S$ = 0.4${\mu }_B$. The origin of the orbital moment is analyzed and understood in terms of additional spin-orbital lowering of symmetry, and beyond that due to structural distortion, for magnetization along [100]. Further interpretation is assisted by analysis of the spin density and the Wannier function with SOC included.

7 pages

References in corpus (3)

• Extremely strong-coupling superconductivity and anomalous lattice properties in the beta-pyrochlore oxide KOs2O6
• Orbital-quenching-induced magnetism in Ba_2NaOsO_6
• Structural and Correlation Effects in the Itinerant Insulating Antiferromagnetic Perovskite NaOsO3

Cited by in corpus (5)

• Emergent odd-parity multipoles and magnetoelectric effects on a diamond structure: implication to 5$d$ transition metal oxides $A$OsO${}_4$ ($A=$ K, Rb, and Cs)
• Spin-orbit coupling, strong correlation, and insulator-metal transitions: the J${}_{\mathrm{eff}}$ =3\2 ferromagnetic Mott insulator Ba${}_2$NaOsO${}_6$
• Frustrated Heisenberg $J_1-J_2$ model within the stretched diamond lattice of LiYbO2
• Crystal structure and the magnetic properties of the 5d transition metal oxide AOsO4 (A = K, Rb, Cs)
• Spin-orbital-momentum locking under odd-parity magnetic quadrupole ordering