236 citations · 309 across the 8 of their papers we have counts for
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Divacancy superstructures in thermoelectric calcium-doped sodium cobaltate
D. G. Porter, M. Roger, M. J. Gutmann +5
We have grown single crystals of NaCaCoO and determined their superstructures as a function of composition using neutron and x-ray diffraction. Inclusion of Ca s…
Crystal-to-stripe reordering of sodium ions in NaxCoO2 (x>=0.75)
D. J. P. Morris, M. Roger, M. J. Gutmann +8
The sodium reordering in NaxCoO2 in the vicinity of room temperature is rationalized at high x in terms of phase transitions between square and striped phases. A striking hexagon-o…
On the Ordering of Na Ions in NaCoO
M. Roger, D. J. P. Morris, D. A. Tennant +8
The influence of electrostatic interactions on the ordering of sodium ions in NaCoO is studied theoretically through Monte-Carlo simulations. For large small di- or tri…
Patterning of sodium ions and the control of electrons in sodium cobaltate
M. Roger, D. J. P. Morris, D. A. Tennant +10
NaxCoO2 has emerged as a material of exceptional scientific interest due to the potential for thermoelectric applications, and because the strong interplay between the magnetic and…
Spin correlations in the paramagnetic phase and ring exchange in lanthanum cuprate
A. M. Toader, J. P. Goff, M. Roger +3
Spin correlations in the paramagnetic phase of lanthanum cuprate have been studied using polarized neutron scattering, with two important results. First, the temperature dependence…
Ring Exchange and Correlated Fermions
Michel Roger
The concept of exchange in strongly-correlated fermions is reviewed with emphasis on the generalization of the Heisenberg pair exchange to higher order n-particle permutations. The…