| 1. |
- Forslund, Ola Kenji, et al.
(författare)
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Revisiting the A-type antiferromagnet NaNiO2 with muon spin rotation measurements and density functional theory calculations
- 2020
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 102:18
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Tidskriftsartikel (refereegranskat)abstract
- An A-type antiferromagnet, NaNiO2, was examined by means of positive muon spin rotation and relaxation (mu+SR) measurements and first-principles calculations based on a density functional theory (DFT). Below T-N = 20 K, a clear muon spin precession signal was observed in the mu+SR time spectrum recorded under zero field, due to the formation of a static internal magnetic field. The microscopic origin of such an internal field was computed as a sum of dipolar and hyperfine contact fields at the site (0.624, 0, 0.854), where both the muon site and the local spin density at such a site were predicted with DFT calculations. While the computed values were consistent with experimentally obtained ones, in both the antiferromagnetic and the paramagnetic states, the contribution of the hyperfine contact field was shown to be insignificant even below T-N. Finally, measurements at higher temperatures signified thermally activated Na-ion diffusion with E-a = 50(20) meV and D-Na(300K) = 8.8 x 10(-11) cm(2)/s, commonly observed in layered-type compounds.
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| 2. |
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| 3. |
- Nozaki, Hiroshi, et al.
(författare)
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Magnetic structure for NaCr2O4 analyzed by neutron diffraction and muon spin-rotation
- 2018
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Ingår i: Physica. B, Condensed matter. - : ELSEVIER SCIENCE BV. - 0921-4526 .- 1873-2135. ; 551, s. 137-141
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the magnetic ground state of a novel one-dimensional compound, NaCr2O4, in which Cr2O4 double chains, i.e. zig-zag chains are aligned parallel to the b-axis, by means of both muon-spin rotation and relaxation (mu+SR) and neutron diffraction (ND) measurements. The mu+SR results reveal the formation of static antiferromagnetic order below Neel temperature (T-N = 124 K). The ND measurements also demonstrate the appearance of magnetic Bragg peaks with the propagation vector (k) over right arrow = (1, 0, 1) below T-N. Combined analyses of the mu+SR and ND data clarify that the Cr moments in each zig-zag chain are aligned ferromagnetically along the c-axis, whereas antiferromagnetically along the alpha-axis between the adjacent zig-zag chains.
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| 4. |
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| 5. |
- Sugiyama, Jun, et al.
(författare)
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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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Ingår i: 20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015. - : Elsevier. ; , s. 868-875
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Konferensbidrag (refereegranskat)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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| 6. |
- Sugiyama, Jun, et al.
(författare)
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Magnetic phases in Sr1-xCaxCo2P2 studied by mu+SR
- 2015
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Ingår i: 20TH INTERNATIONAL CONFERENCE ON MAGNETISM, ICM 2015. - : Elsevier. ; , s. 426-434
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Konferensbidrag (refereegranskat)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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| 7. |
- Sugiyama, Jun, et al.
(författare)
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Magnetism of the A-site ordered perovskites CaCu3Cr4O12 and LaCu3Cr4O12
- 2018
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 97:2
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Tidskriftsartikel (refereegranskat)abstract
- The microscopic magnetic nature of the A-site ordered chromium perovskites CaCu3Cr4O12 and LaCu3Cr4O12 and their solid-solution system, Ca1-x LaxCu3Cr4O12, with x = 0.2, 0.4, and 0.8, has been studied with muon spin rotation and relaxation (mu+SR) measurements down to 2 K using a powder sample. For CaCu3Cr4O12, mu+SR revealed the formation of static antiferromagnetic (AF) order below 122 K (=T-N), although magnetization measurements showed a very small change at T-N. Analyses of the internal magnetic field H-int at the muon sites, predicted with first-principles calculations, suggested G-type AF order as a ground state. For LaCu3Cr4O12 with T-N = 225 K, mu+SR also supported the presence of aG-type AF ordered state, which was recently proposed based on neutron diffraction measurements. However, the ordered Cr moments were found to change the direction at around 10 K. For Ca1-xLaxCu3Cr4O12, both T-N and H-int at 2 K increase monotonically with x.
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| 8. |
- Sugiyama, Jun, et al.
(författare)
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Variation of magnetic ground state of Sr1-xCaxCo2P2 determined with mu(+) SR
- 2015
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 91:14
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Tidskriftsartikel (refereegranskat)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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