Investigation of the Spin Density Wave in NaxCoO2

Abstract

Magnetic susceptibility, transport and heat capacity measurements of single crystal NaxCoO2 (x=0.71) are reported. A transition to a spin density wave (SDW) state at Tmag = 22 K is observable in all measurements, except chi(ac) data in which a cusp is observed at 4 K and attributed to a low temperature glassy phase. M(H) loops are hysteretic below 15 K. Both the SDW transition and low temperature hysteresis are only visible along the c-axis. The system also exhibits a substantial (~40%) positive magnetoresistance below this temperature. Calculations of the electronic heat capacity gamma above and below Tmag and the size of the jump in C indicate that the onset of the SDW brings about the opening of gap and the removal of part of the Fermi surface. Reduced in-plane electron-electron scattering counteracts the loss of carriers below the transition and as a result we see a net reduction in resistivity below Tmag. Sodium ordering transitions at higher temperatures are observable as peaks in the heat capacity with a corresponding increase in resistivity.

14 pages, 6 figures

References in corpus (11)

• Spin entropy as the likely source of enhanced thermopower in $\rm\bf Na_xCo_2O_4
• Charge-ordering, commensurability and metallicity in the phase diagram of layered Na(x)CoO(2)
• Bulk antiferromagnetism in $\mathbf{N}{\mathbf{a}}_{0.82}\mathbf{Co}{\mathbf{O}}_2$ single crystals
• Magnetic susceptibility study of hydrated and non-hydrated NaxCoO2-yH2O single crystals
• Structural transition in NaxCoO2 with x near 0.75 due to Na rearrangement
• Synthesis, Characterization, and Magnetic Properties of gamma-NaxCoO2 (0.70 < x <0.84)
• Thermal and Electrical Properties of gamma-NaxCoO2 (0.70 < x < 0.78)
• Anomalous high-temperature Hall effect on the triangular lattice in Na_xCoO_2
• Evidence for two electronic components in NaxCoO2 (x = 0.7-0.75)
• Magnetic Studies of Polycrystalline and Single-Crystal NaxCoO2
• Evidence and Characterization of a SDW Transition in Na0.75CoO2 Single Crystals

Cited by in corpus (10)

• Non-magnetic insulator state in Na1CoO2 and phase separation of Na vacancies
• Electronic texture of the thermoelectric oxide Na0.75CoO2
• Direct link between low temperature magnetism and high temperature sodium order in NaxCoO2
• Elliptical hole pockets in the Fermi surfaces of unhydrated and hydrated sodium cobalt oxides
• Magnetism and Ion Diffusion in Honeycomb Layered Oxide K${}_2$Ni${}_2$TeO${}_6$: First Time Study by Muon Spin Rotation & Neutron Scattering
• Crystal-to-stripe reordering of sodium ions in NaxCoO2 (x>=0.75)
• Spin fluctuations, magnetic long-range order and Fermi surface gapping in NaxCoO2
• Phase segregation in NaxCoO2 for large Na contents
• Interplay between mesoscopic phase separation and bulk magnetism in the layered NaxCoO2
• The magnetic field and pressure dependence of the magnetic ordering transition in NaxCoO2 (0.6<x<0.72)