Static magnetic order in Na0.75CoO2 detected by muon spin rotation and relaxation

Jun Sugiyama, Hiroshi Itahara, Jess H. Brewer, Eduardo J. Ansaldo, Teruki Motohashi, Maarit Karppinen, Hisao Yamauchi

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105 Citations (Scopus)


The nature of the magnetic transition of the Na-rich thermoelectric Na0.75CoO2 at 22 K was studied by positive muon-spin-rotation and relaxation (μ+SR) spectroscopy, using a polycrystalline sample in the temperature range between 300 and 2.5 K. Zero-field μSR measurements indicated the existence of a static internal magnetic field at temperatures below 22 K (= Tm). The observed muon-spin precession signal below Tm consisted of three components with different precession frequencies, corresponding to three inequivalent μ+ sites in the Na0.75CoO2 lattice. The total volume fraction of the three components was estimated as 21% at 2.5 K; thus, this magnetic transition was not induced by impurities but is an intrinsic change in the magnetism of the sample, although the sample was magnetically inhomogeneous otherwise. On the other hand, a similar experiment on a Na0.65CoO2 sample exhibited no magnetic transition down to 2.5 K; which indicates that the average valence of the Co ions is responsible for inducing the magnetic transition at 22 K.

Original languageEnglish
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number21
Publication statusPublished - 17 Jun 2003
MoE publication typeA1 Journal article-refereed

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