Half-magnetization plateau and the origin of threefold symmetry breaking in an electrically switchable triangular antiferromagnet

Abstract

We perform high-field magnetization measurements on the triangular lattice antiferromagnet Fe 1/3 NbS 2. We observe a plateau in the magnetization centered at approximately half the saturation magnetization over a wide range of temperature and magnetic field. From density functional theory calculations, we determine a likely set of magnetic exchange constants. Incorporating these constants into a minimal Hamiltonian model of our material, we find that the plateau and the Z 3 symmetry-breaking ground state both arise from the competition of interplane and intraplane exchange interactions. These findings are pertinent to the magnetoelectric properties of Fe 1/3 NbS 2 , which allow electrical switching of antiferromagnetic textures at relatively low current densities.

Exchange bias due to coupling between coexisting antiferromagnetic and spin-glass orders

“…Single crystals were synthesized using conventional vapor transport techniques while varying concentrations of iron (see supplement sections 1-6 for characterization of homogeneity and stoichiometry). This material manifests AFM hexagonal ordering [18][19][20] with the moment predominantly oriented along the c-axis. For intercalation values less than x = 1 3 , SGlike behavior has been observed in magnetization and heat capacity measurements.…”

“…[21][22][23] Magnetization versus temperature measurements performed along the c-axis on x ≈ 1 3 , corresponding to the fully packed Fe 1/3 NbS 2 structure, we observe a sharp AFM transition with a Néel temperature of approximately 42 K (see supplement section 14) as has been previously reported. [20,22,[24][25][26] Above or below x = 1 3 , field cooled (FC) and zero field cooled (ZFC) curves begin to separate, indicating the presence of a frozen moment.…”

“…This motivates us to study the exchange bias at magnetic fields high enough to drive a metamagnetic transition in the AFM. [20] It has been recently shown that the AFM of the stoichiometric compound undergoes a metamagnetic transition from stripe to an up-up-updown phase at H plat ∼ 17 T, which is characterized by a plateau in the magnetization. [20] This same transition is observed at all compositions, albeit greatly broadened by disorder due to the deviation from x = 1 3 .…”

“…[20] It has been recently shown that the AFM of the stoichiometric compound undergoes a metamagnetic transition from stripe to an up-up-updown phase at H plat ∼ 17 T, which is characterized by a plateau in the magnetization. [20] This same transition is observed at all compositions, albeit greatly broadened by disorder due to the deviation from x = 1 3 . As shown in Figure 5, hysteresis loops close only at fields that go well beyond the metamagnetic transition for any composition -the hysteretic response of the SG is coupled to the magnetic response of the AFM.…”

Origins of anisotropic transport in the electrically switchable antiferromagnet Fe1/3NbS2

“…Given the limitations of PBE+U , to gain confidence in consistent qualitative features in transport anisotropy we perform and describe PBE+U calculations using two different U values in the main text. We first use PBE+U with U = 0.3, eV following previous work, which results in a magnetoanisotropy energy (MAE) consistent with experiment [30]. However, as we noted in Ref.…”