Direct link between low-temperature magnetism and high-temperature sodium order in NaxCoO2.
We prove the direct link between low-temperature (T) magnetism and high-T Na+ ordering in NaxCoO2 using the example of a so far unreported magnetic transition at 8 K which involves a weak ferromagnetic moment. The 8 K feature is characterized in detail and its dependence on a diffusive Na+ rearrangement around 200 K is demonstrated. Applying muons as local probes this process is shown to result in a reversible phase separation into distinct magnetic phases that can be controlled by specific cooling protocols. Thus the impact of ordered Na+ Coulomb potential on the CoO2 physics is evidenced opening new ways to experimentally revisit the NaxCoO2 phase diagram.
Schulze
T F
TF
Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich, Switzerland. tschulze@phys.ethz.ch
Häfliger
P S
PS
Niedermayer
Ch
Ch
Mattenberger
K
K
Bubenhofer
S
S
Batlogg
B
B