Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Toward cubic symmetry for Ir$^{4+}$: structure and magnetism of
  antifluorite K$_2$IrBr$_6$   Crystal structure, electronic state of Ir$^{4+}$, and magnetic properties of
the antifluorite compound K$_2$IrBr$_6$ are studied using high-resolution
synchrotron x-ray diffraction, resonant inelastic x-ray scattering (RIXS),
thermodynamic and transport measurements, and ab initio calculations. The
crystal symmetry is reduced from cubic at room temperature to tetragonal below
170 K and eventually to monoclinic below 122 K. These changes are tracked by
the evolution of the non-cubic crystal-field splitting $\Delta$ measured by
RIXS. Non-monotonic changes in $\Delta$ are ascribed to the competing effects
of the tilt, rotation, and deformation of the IrBr$_6$ octahedra as well as
tetragonal strain on the electronic levels of Ir$^{4+}$. The N\'eel temperature
of $T_N=11.9$ K exceeds that of the isostructural K$_2$IrCl$_6$, and the
magnitude of frustration on the fcc spin lattice decreases. We argue that the
replacement of Cl by Br weakens electronic correlations and enhances magnetic
couplings.

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The categories of this paper are: eess
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The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
27
The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
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The categories of this paper are: econ
6
The categories of this paper are: astro-ph
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
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The categories of this paper are: mtrl-th
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The categories of this paper are: chao-dyn