Spin state transition in Ca-doped Na0.7CoO2 with the nominal Co valence below 3.16

J. Sugiyama; J. H. Brewer; E. J. Ansaldo; J. A. Chakhalian; H. Nozaki; H. Hazama; Y. Ono; T. Kajitani

doi:10.1016/j.ssc.2005.10.014

Spin state transition in Ca-doped Na_0.7CoO₂ with the nominal Co valence below 3.16

J. Sugiyama, J. H. Brewer, E. J. Ansaldo, J. A. Chakhalian, H. Nozaki, H. Hazama, Y. Ono, T. Kajitani

Research output: Contribution to journal › Article › peer-review

3 Scopus citations

Abstract

In order to clarify the nature of the transition around 300 K in Ca-doped Na_0.7CoO₂, the magnetism of Na_0.7Ca _yCoO₂ with y=0.035 and 0.07 was investigated in a positive muon spin rotation and relaxation (μ⁺SR) experiment. Transverse field μ⁺SR measurements showed that the spin state of the Co ions in Na_0.7Ca_0.07CoO₂ changes at around 300 K; i.e. the exponential relaxation rate vs. T curve exhibited a large maximum around 300 K with an accompanying small peak in the muonic Knight shift, whereas no changes were found in the asymmetry, similar to [Ca₂CoO ₃]_0.62[CoO₂] at around 400 K. Although the spin-density-wave (SDW) state exists for Na_xCoO₂ with x≥0.75 at low temperatures, zero-field μ⁺SR spectra in the Ca-doped samples showed no muon spin precessions down to 1.8 K but only fast relaxations indicating disorder. This is probably because the Ca²⁺ ions in the Na planes alter the charge and/or spin distribution in the CoO ₂ planes. As a result, the SDW order is hindered, as the nominal Co valence is decreased below 3.16.

Original language	English (US)
Pages (from-to)	36-40
Number of pages	5
Journal	Solid State Communications
Volume	137
Issue number	1-2
DOIs	https://doi.org/10.1016/j.ssc.2005.10.014
State	Published - Jan 2006
Externally published	Yes

All Science Journal Classification (ASJC) codes

Chemistry(all)
Condensed Matter Physics
Materials Chemistry

Keywords

A. Layered cobalt oxides
D. Muon spin rotation and relaxation
D. Spin state transition
D. Thermoelectrics

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@article{a9f2be43da364648a9c39974a75ac822,

title = "Spin state transition in Ca-doped Na0.7CoO2 with the nominal Co valence below 3.16",

abstract = "In order to clarify the nature of the transition around 300 K in Ca-doped Na0.7CoO2, the magnetism of Na0.7Ca yCoO2 with y=0.035 and 0.07 was investigated in a positive muon spin rotation and relaxation (μ+SR) experiment. Transverse field μ+SR measurements showed that the spin state of the Co ions in Na0.7Ca0.07CoO2 changes at around 300 K; i.e. the exponential relaxation rate vs. T curve exhibited a large maximum around 300 K with an accompanying small peak in the muonic Knight shift, whereas no changes were found in the asymmetry, similar to [Ca2CoO 3]0.62[CoO2] at around 400 K. Although the spin-density-wave (SDW) state exists for NaxCoO2 with x≥0.75 at low temperatures, zero-field μ+SR spectra in the Ca-doped samples showed no muon spin precessions down to 1.8 K but only fast relaxations indicating disorder. This is probably because the Ca2+ ions in the Na planes alter the charge and/or spin distribution in the CoO 2 planes. As a result, the SDW order is hindered, as the nominal Co valence is decreased below 3.16.",

keywords = "A. Layered cobalt oxides, D. Muon spin rotation and relaxation, D. Spin state transition, D. Thermoelectrics",

author = "J. Sugiyama and Brewer, {J. H.} and Ansaldo, {E. J.} and Chakhalian, {J. A.} and H. Nozaki and H. Hazama and Y. Ono and T. Kajitani",

note = "Funding Information: We thank S.R. Kreitzman, B. Hitti, and D.J. Arseneau of TRIUMF for help with the μSR experiments. Also, we appreciate Y. Miyazaki of Tohoku Univ., T. Tani and R. Asahi of Toyota CRDL., U. Mizutani, H. Ikuta and T. Takeuchi of Nagoya Univ. for discussions. This work was supported at Toyota CRDL by joint research and development with the International Center for Environmental Technology Transfer in 2002–2004, commissioned by the Ministry of Economy Trade and Industry of Japan, at UBC by the Canadian Institute for Advanced Research and the Natural Sciences and Engineering Research Council of Canada, and at TRIUMF by the National Research Council of Canada.",

year = "2006",

month = jan,

doi = "10.1016/j.ssc.2005.10.014",

language = "English (US)",

volume = "137",

pages = "36--40",

journal = "Solid State Communications",

issn = "0038-1098",

publisher = "Elsevier Limited",

number = "1-2",

}

TY - JOUR

T1 - Spin state transition in Ca-doped Na0.7CoO2 with the nominal Co valence below 3.16

AU - Sugiyama, J.

AU - Brewer, J. H.

AU - Ansaldo, E. J.

AU - Chakhalian, J. A.

AU - Nozaki, H.

AU - Hazama, H.

AU - Ono, Y.

AU - Kajitani, T.

N1 - Funding Information: We thank S.R. Kreitzman, B. Hitti, and D.J. Arseneau of TRIUMF for help with the μSR experiments. Also, we appreciate Y. Miyazaki of Tohoku Univ., T. Tani and R. Asahi of Toyota CRDL., U. Mizutani, H. Ikuta and T. Takeuchi of Nagoya Univ. for discussions. This work was supported at Toyota CRDL by joint research and development with the International Center for Environmental Technology Transfer in 2002–2004, commissioned by the Ministry of Economy Trade and Industry of Japan, at UBC by the Canadian Institute for Advanced Research and the Natural Sciences and Engineering Research Council of Canada, and at TRIUMF by the National Research Council of Canada.

PY - 2006/1

Y1 - 2006/1

N2 - In order to clarify the nature of the transition around 300 K in Ca-doped Na0.7CoO2, the magnetism of Na0.7Ca yCoO2 with y=0.035 and 0.07 was investigated in a positive muon spin rotation and relaxation (μ+SR) experiment. Transverse field μ+SR measurements showed that the spin state of the Co ions in Na0.7Ca0.07CoO2 changes at around 300 K; i.e. the exponential relaxation rate vs. T curve exhibited a large maximum around 300 K with an accompanying small peak in the muonic Knight shift, whereas no changes were found in the asymmetry, similar to [Ca2CoO 3]0.62[CoO2] at around 400 K. Although the spin-density-wave (SDW) state exists for NaxCoO2 with x≥0.75 at low temperatures, zero-field μ+SR spectra in the Ca-doped samples showed no muon spin precessions down to 1.8 K but only fast relaxations indicating disorder. This is probably because the Ca2+ ions in the Na planes alter the charge and/or spin distribution in the CoO 2 planes. As a result, the SDW order is hindered, as the nominal Co valence is decreased below 3.16.

AB - In order to clarify the nature of the transition around 300 K in Ca-doped Na0.7CoO2, the magnetism of Na0.7Ca yCoO2 with y=0.035 and 0.07 was investigated in a positive muon spin rotation and relaxation (μ+SR) experiment. Transverse field μ+SR measurements showed that the spin state of the Co ions in Na0.7Ca0.07CoO2 changes at around 300 K; i.e. the exponential relaxation rate vs. T curve exhibited a large maximum around 300 K with an accompanying small peak in the muonic Knight shift, whereas no changes were found in the asymmetry, similar to [Ca2CoO 3]0.62[CoO2] at around 400 K. Although the spin-density-wave (SDW) state exists for NaxCoO2 with x≥0.75 at low temperatures, zero-field μ+SR spectra in the Ca-doped samples showed no muon spin precessions down to 1.8 K but only fast relaxations indicating disorder. This is probably because the Ca2+ ions in the Na planes alter the charge and/or spin distribution in the CoO 2 planes. As a result, the SDW order is hindered, as the nominal Co valence is decreased below 3.16.

KW - A. Layered cobalt oxides

KW - D. Muon spin rotation and relaxation

KW - D. Spin state transition

KW - D. Thermoelectrics

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U2 - 10.1016/j.ssc.2005.10.014

DO - 10.1016/j.ssc.2005.10.014

M3 - Article

AN - SCOPUS:28844466077

VL - 137

SP - 36

EP - 40

JO - Solid State Communications

JF - Solid State Communications

SN - 0038-1098

IS - 1-2

ER -