SciPost Phys. 5, 063 (2018) ·
published 18 December 2018

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Mn$_{3}$X (X= Sn, Ge) are noncollinear antiferromagnets hosting a large
anomalous Hall effect (AHE). Weyl nodes in the electronic dispersions are
believed to cause this AHE, but their locus in the momentum space is yet to be
pinned down. We present a detailed study of the Hall conductivity tensor and
magnetization in Mn$_{3}$Sn crystals and find that in the presence of a
moderate magnetic field, spin texture sets the orientation of the $k$space
Berry curvature with no detectable inplane anisotropy due to the $Z_6$
symmetry of the underlying lattice. We quantify the energy cost of domain
nucleation and show that themultidomain regime is restricted to a narrow field
window. Comparing the field dependence of AHE and magnetization, we find that
there is a distinct component in the AHE which does not scale with
magnetization when the domain walls are erected. This socalled `topological'
Hall effect provides indirect evidence for a noncoplanar spin components and
realspace Berry curvature in domain walls.
SciPost Phys. 5, 020 (2018) ·
published 5 September 2018

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I study the structural and magnetic instabilities in LaNiO$_3$ using density
functional theory calculations. From the nonspinpolarized structural
relaxations, I find that several structures with different Glazer tilts lie
close in energy. The $Pnma$ structure is marginally favored compared to the
$R\overline{3}c$ structure in my calculations, suggesting the presence of
finitetemperature structural fluctuations and a possible proximity to a
structural quantum critical point. In the spinpolarized relaxations, both
structures exhibit the $\uparrow\!\!0\!\!\downarrow\!\!0$ antiferromagnetic
ordering with a rocksalt arrangement of the octahedral breathing distortions.
The energy gain due to the breathing distortions is larger than that due to the
antiferromagnetic ordering. These phases are semimetallic with small
threedimensional Fermi pockets, which is largely consistent with the recent
observation of the coexistence of antiferromagnetism and metallicity in
LaNiO$_3$ single crystals by Guo et al. [Nat. Commun. 9, 43 (2018)].
Dr Subedi: "I'd like to correct three smal..."
in Submission on Breathing distortions in the metallic, antiferromagnetic phase of LaNiO$_3$ by Alaska Subedi