Complex magnetic differentiation of cobalts in NaxCoO2 with 22 K Néel temperature
I. R. Mukhamedshin+*, I. F. Gilmutdinov+, M. A. Salosin+, H. Alloul*
+Institute of Physics, Kazan Federal University, 420008 Kazan, Russia
*Laboratoire de Physique des Solides, CNRS UMR 8502, UniversitéParis-Sud, 91405 Orsay, France, EU
Single crystals of sodium cobaltates NaxCoO2
with were grown by the floating zone technique. Using electrochemical
Na de-intercalation method we reduced the sodium content in the as-grown
crystals down to pure phase with 22 K Néel temperature and
. The 59Co NMR study
in the paramagnetic state of the TN=22 K
phase permitted us to evidence that at least 6 Co sites are differentiated.
They could be separated by their magnetic behaviour into three types: a
single site with cobalt close to non-magnetic Co3+, two sites with the
most magnetic cobalts in the system, and the remaining three sites displaying
an intermediate behaviour. This unusual magnetic differentiation calls for
more detailed NMR experiments on our well characterized samples.