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Theory of charge and spin ordering in the nickelates - Physics ...

Theory of charge and spin ordering in the nickelates - Physics ...

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Valence skipp<strong>in</strong>g<br />

Maz<strong>in</strong> et al, 2007: <strong>the</strong>oretically suggest mixed<br />

valence PRL 98, state 176406 to (2007) enhance exchange<br />

FIG. 1 (color onl<strong>in</strong>e). Schematic electronic level diagram <strong>of</strong> Ni<br />

But: Why <strong>the</strong> complex magnetic <strong>order<strong>in</strong>g</strong><br />

ions <strong>in</strong> RNiO 3 <strong>in</strong> two cases: (a) two JT distorted Ni<br />

pattern?<br />

3 ions<br />

(energy ga<strong>in</strong> E JT per site), <strong>and</strong> (b) <strong>charge</strong> disproportionation.<br />

c.f. Mizokawa, Khomskii, Sawatzky, 2000<br />

<strong>and</strong> <strong>in</strong> <strong>the</strong> fully delocalized limit, <strong>the</strong> additional Coulomb<br />

energy due to CO is reduced to <strong>the</strong> Hartree energy, a very<br />

strong reduction. Fur<strong>the</strong>rmore, delocalization <strong>of</strong>ten leads<br />

PHYSICAL REVIEW LETTERS<br />

even <strong>the</strong> magnetic <strong>in</strong>st<br />

paramagnetic metal do<br />

disproportionation. Ex<br />

manifests itself <strong>in</strong> oxyg<br />

netic moments on <strong>the</strong> tw<br />

contrary to popular be<br />

Mott-Hubbard <strong>in</strong>sulato<br />

The <strong>in</strong>sulator-metal<br />

structure <strong>in</strong> RNiO 3 are<br />

0:7 B for Ni 2 <strong>in</strong> YNi<br />

1:4 B <strong>and</strong> 0:6 B for H<br />

A close <strong>in</strong>spection<br />

tional b<strong>and</strong> picture give<br />

it is capable <strong>of</strong> expla<br />

occurs <strong>in</strong> <strong>the</strong> crossover<br />

erant states along <strong>the</strong><br />

b<strong>and</strong> structure calculat<br />

zation <strong>of</strong> <strong>the</strong> nonmag

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