| 1. |
- Sugiyama, Jun, et al.
(author)
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Magnetic ground state of novel zigzag chain compounds, NaCr2O4 and Ca1-xNaxCr2O4, determined with muons and neutrons
- 2015
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In: 20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015. - : Elsevier. ; , s. 868-875
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Conference paper (peer-reviewed)abstract
- The magnetic nature of a novel one-dimensional compound NaCr2O4 with zigzag CrO2 chains has been studied by muon spin rotation and relaxation (mu+SR) and neutron diffraction (ND). It is found that NaCr2O4 undergoes an antiferromagnetic transition at T-N = 125 K, below which the Cr moments in each zigzag chain align ferromagnetically along the c-axis but antiferromagnetically along the a-axis between adjacent zigzag chains. For the solid solution system Ca1-xNaxCr2O4, mu+SR measurements reveal the evolution of a complex magnetic order with increasing Ca content (1 - x), which finally enters into an incommensurate AF ordered state below T-N = 21 for CaCr2O4.
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| 2. |
- Sugiyama, Jun, et al.
(author)
-
Magnetic phases in Sr1-xCaxCo2P2 studied by mu+SR
- 2015
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In: 20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015. - : Elsevier. ; , s. 426-434
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Conference paper (peer-reviewed)abstract
- In order to elucidate the dependence of the magnetic ground state on the Ca content (x) in Sr1-xCaxCo2P2 (0 <= x <= 1, ThCr2Si2-type structure), we have performed muon spin rotation and relaxation (mu+SR) experiments on Sr1-xCaxCo2P2 powder samples mainly in a zero applied field. The end member compound, SrCo2P2, is found to be paramagnetic down to 19 mK. As x increases, such a paramagnetic ground state is observed down to 1.8 K until x = 0.45. Then, as x increases further, a short-range antiferromagnetic (AF) ordered phase appears at low temperatures for 0.48 <= x <= 0.75, and finally, a long-range AF ordered phase is stabilized for x > 0.75. The internal magnetic field of the other end member compound, CaCo2P2, is well consistent with that of the A-type AF order state, which was proposed from neutron scattering experiments. The phase diagram determined with mu+SR is different from that proposed by macroscopic measurements. For an isostructural compound, LaCo2P2, static magnetic order is found to be formed below similar to 130 K.
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| 3. |
- Sugiyama, Jun, et al.
(author)
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Variation of magnetic ground state of Sr1-xCaxCo2P2 determined with mu(+) SR
- 2015
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 91:14
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Journal article (peer-reviewed)abstract
- In order to study the variation of a microscopic internal magnetic field with the Ca content (x), we have systematically measured muon-spin rotation and relaxation (mu+SR) spectra for Sr1-xCaxCo2P2 (0 <= x <= 1) powder samples mainly in a zero external field. As x increases from 0, a Pauli-paramagnetic phase is observed even at the lowest T measured (1.8 K) until x = 0.45; then, a short-range antiferromagnetic (AF) ordered phase appears for 0.48 <= x <= 0.75, and finally a long-range AF ordered phase is stabilized for x >= 0.75. The evolution of the magnetic order is connected to the shrinking of the c-axis length as a function of x, which naturally enhances the AF interaction between the two adjacent Co planes.
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| 4. |
- Umegaki, Izumi, et al.
(author)
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Battery Materials Research with Muon Beam
- 2019
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In: Proceedings of the 3rd International Symposium of Quantum Beam Science at Ibaraki University "Quantum Beam Science in Biology and Soft Materials (ISQBSS2018). - : Physical society of Japan.
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Conference paper (peer-reviewed)abstract
- We applied a positive muon spin rotation and relaxation (μ+SR) technique to battery materials research by investigating Li diffusion in cathode and electrolyte materials. Recently, we have found that Li diffusion in graphite, which is commonly used as an anode material in Li-ion batteries, is detectable with μ+SR. Following upon the initial μ+SR measurements on the Li intercalated graphites, C6Li and C12Li, μ+SR spectra were also measured for C12Li0.92 and C18Li0.90 posing a slightly different occupancy in the same stage structure as those of C6Li and C12Li. The temperature dependence of diffusive nature in C12Li0.92 and C18Li0.90 was found to be similar in nature to those in C6Li and C12Li. Such a diffusion was found to start to occur approximately by 50 K lower than those of C6Li and C12Li. This suggests that Li starts to diffuse at lower temperatures in the nonstoichiometric Li intercalated graphite samples than that in the stoichiometric samples.
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| 5. |
- Umegaki, Izumi, et al.
(author)
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Li-ion diffusion in Li intercalated graphite C6Li and C12Li probed by mu+SR
- 2017
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In: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 19:29, s. 19058-19066
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Journal article (peer-reviewed)abstract
- In order to study a diffusive behavior of Li+ in Li intercalated graphites, we have measured muon spin relaxation (mu+SR) spectra for C6Li and C12Li synthesized with an electrochemical reaction between Li and graphite in a Li-ion battery. For both compounds, it was found that Li+ ions start to diffuse above 230 K and the diffusive behavior obeys a thermal activation process. The activation energy (E-a) for C6Li is obtained as 270(5) meV, while E-a = 170(20) meV for C12Li. Assuming a jump diffusion of Li+ in the Li layer of C6Li and C12Li, a self-diffusion coefficient D-Li at 310 K was estimated as 7.6(3) x 10(-11) (cm(2) s(-1)) in C6Li and 14.6(4) x 10(-11) (cm(2) s(-1)) in C12Li.
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