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

Abstract

Recent experiments on the antiferromagnetic intercalated transition metal dichalcogenide Fe 1/3 NbS 2 have demonstrated reversible resistivity switching by application of orthogonal current pulses below its magnetic ordering temperature, making Fe 1/3 NbS 2 promising for spintronics applications. Here, we perform density functional theory calculations with Hubbard U corrections of the magnetic order, electronic structure, and transport properties of crystalline Fe 1/3 NbS 2 , clarifying the origin of the different resistance states. The two experimentally proposed antiferromagnetic ground states, corresponding to in-plane stripe and zigzag ordering, are computed to be nearly degenerate. In-plane cross sections of the calculated Fermi surfaces are anisotropic for both magnetic orderings, with the degree of anisotropy sensitive to the Hubbard U value. The in-plane resistance, computed within the Kubo linear response formalism using a constant relaxation time approximation, is also anisotropic, supporting a hypothesis that the current-induced resistance changes are due to a repopulating of antiferromagnetic domains. Our calculations indicate that the transport anisotropy of Fe 1/3 NbS 2 in the zigzag phase is reduced relative to stripe, consistent with the relative magnitudes of resistivity changes in experiment. Finally, our calculations reveal the likely directionality of the current-domain response, specifically, which domains are energetically stabilized for a given current direction.

Long-range, Non-local Switching of Spin Textures in a Frustrated Antiferromagnet

“…composition x > 1 /3 [6]. According to a recent DFT study, which explores the Fermi surface anisotropies of the domains of the respective phases, [1] this likely explains the opposite switching responses in identical device geometries, as shown in Fig. 1(a),(b).…”

“…(e) Similarly in zigzag-dominated samples, a horizontal current pulse favors domains whose principal axes are not parallel to the pulse, and (f) a vertical current pulse favors the domain whose principal axis is perpendicular to the current pulse direction. The domain configurations in panels (c) and (e) have opposite conductivity anisotropies, as do those in panels (d) and (f) [1], so that (g) when stripe and zig-zag orders coexist, there will be competing switching responses, as shown schematically in (h). Note the similarity with the black curve with the observed signal in Fig.…”

“…1(c)-(f), for each different kind of magnetic order. A given direction of switching pulse j destabilizes domains whose principal axes are parallel to the applied current, [1,7] so that a pulse in the [100] direction will strongly disfavor one specific stripy domain (Fig. 1 (d)) and one specific zig-zag domain (Fig.…”

“…1(f).) With respect to the principal axes, the conductivity tensor components σ xx > σ yy for stripe domains and σ xx < σ yy for zigzag domains, so when the current is applied along 45 • , this leads to opposite switching responses in the off-diagonal conductivity [1]. At compositions where the order parameters are comparable in magnitude, one would expect the response to vanish -and…”

Structure and Magnetism of Iron- and Chromium-Intercalated Niobium and Tantalum Disulfides

“…81 Furthermore, DFT calculations conclude that the two phases are nearly degenerate, such that their relative stability depends on computational choices such as the Hubbard U-parameter. 82 Other computational work suggests that the stripe-phase is appreciably lower in energy and that the three-phase metamagnetic structure is reproduced only for the stripe ground state, albeit using a relatively small parameterized model. 79 Accordingly, there is debate within the literature regarding the true nature of the ground state.…”