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

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Magnetic structures Refinements give no materials with momentless Ni sites material m1(µB) m2(µB) Reference Ho 1.4 0.6 PRB 64, 144417 (2001) Y 1.4 0.7 PRL 82, 3871 (1999) Eu 1.2 1.2 PRB 57, 456(1998) Sm 0.9 0.9* PRB 57, 456(1998) Nd 0.9 0.9* PRB 50, 978 (1994) Pr 0.9 0.9* PRB 50, 978 (1994) * observed charge order is inconsistent with equal moments
1918 J B Good Orthorhombic Distortion orthorhombicity Figure 2. Cooperative MX 6/2 rotations giving (a) tetragonal (projection on (001) of MX 3 (b) rhombohedral and (c) orthorhombic (Pbnm axes) symmetry. Note: Pbnm axes a, b, c, b c, a, b, in Pnma. The equilibrium (A–X) and (M–X) bond lengths are calculated for ambient cond from the sums of the ionic radii available in tables [1]; they were obtained from x-ray data
Page 1 and 2: Theory of charge and spin ordering
Page 3 and 4: Outline Introduction to Mott transi
Page 5 and 6: ates remain temperature ds, the key
Page 7 and 8: Bulk transitions Transitions are al
Page 9 and 10: Magnetic structure Neutron scatteri
Page 11 and 12: Charge and spin order CO CO+AF Torr
Page 13 and 14: Valence skipping Mazin et al, 2007:
Page 17 and 18: Hubbard Model A minimal model to co
Page 19 and 20: Phase Diagram Which is more appropr
Page 21 and 22: Tight-binding model Keep just σ-bo
Page 23 and 24: Fermi surfaces Variation with t’/
Page 25 and 26: Nesting Large fermi surface contain
Page 27 and 28: Hartree-Fock Two SDW phases appear
Page 29 and 30: Landau Theory SDW order parameter i
Page 31 and 32: Cubic symmetry Landau free energy F
Page 33 and 34: Cubic symmetry Landau free energy F
Page 35: Cubic lattice “site centered”
Page 39 and 40: SDW states Look along axis θ=0 θ
Page 41 and 42: Hartree-Fock With orthorhombicity,
Page 43 and 44: Back to the Mott Transition What ab
Page 45 and 46: Strong Coupling Approach Consider p
Page 47 and 48: Ordering of pairs Half of sites sho
Page 49 and 50: Magnetism The spin of each Ni 2+ el
Page 51 and 52: Put it together Strong coupling pic
Page 55 and 56: Electronic structure Another way to
Page 57 and 58: Hartree-Fock graphene-like band str
Page 59 and 60: Anisotropy SDW wavevectors cubic un
Page 61 and 62: Nesting Confinement affects Fermi s
Page 63: Summary Theory of the nickelates mu

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

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