| 1. |
- Cedervall, Johan, et al.
(författare)
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Magnetic property changes of NdGa upon hydrogen absorption
- 2024
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 109:13
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Tidskriftsartikel (refereegranskat)abstract
- Rare earth monogallide (REGa) Zintl phases are attractive for their properties in hydrogen storage and magnetic cooling. However, the magnetic effects upon hydrogen additions in REGa are not well understood. This study aims to explore the magnetic effects in REGaHx using SQUID magnetometry and neutron powder diffraction. To avoid challenges due to absorption and high incoherent scattering in the neutron diffraction experiments, the compound NdGaDx (x = 0, 0.9, or 1.6) was chosen for examination. It was found that NdGa exhibits two ferromagnetic structures below the Curie temperature of 42 K. Just below 42 K the magnetic moments are oriented along the crystallographic c axis, and at 20 K a spin reorientation occurs where the moments turn similar to 30 degrees toward the a axis. Upon partial deuteration (x = 0.9), the magnetization decreases and two magnetic phases are observed, one intermediate incommensurate phase, and one canted ferromagnetic phase with the net magnetization aligning along the b axis. For the full deuteride (x = 1.6) only one incommensurate magnetic phase is observed at low temperatures. Magnetometry also reveals that there are no isotope effects when absorbing H or D. The absorption of H or D changes the Nd-Nd distances as well as the electronic structure, which results in a drastic change in the magnetic properties as compared to NdGa.
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| 2. |
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| 3. |
- Miniotaite, Ugne, et al.
(författare)
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Magnetic Properties of Multifunctional (LiFePO4)-Li-7 under Hydrostatic Pressure
- 2023
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Ingår i: Proceedings 15th International Conference on Muon Spin Rotation, Relaxation and Resonance (SR). - : IOP Publishing.
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Konferensbidrag (refereegranskat)abstract
- LiFePO4 (LFPO) is an archetypical and well-known cathode material for rechargeable Li-ion batteries. However, its quasi-one-dimensional (Q1D) structure along with the Fe ions, LFPO also displays interesting low-temperature magnetic properties. Our team has previously utilized the muon spin rotation (mu+SR) technique to investigate both magnetic spin order as well as Li-ion diffusion in LFPO. In this initial study we extend our investigation and make use of high-pressure mu+SR to investigate effects on the low-T magnetic order. Contrary to theoretical predictions we find that the magnetic ordering temperature as well as the ordered magnetic moment increase at high pressure (compressive strain).
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| 4. |
- Nocerino, Elisabetta, et al.
(författare)
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Competition between magnetic interactions and structural instabilities leading to itinerant frustration in the triangular lattice antiferromagnet LiCrSe2
- 2023
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Ingår i: Communications Materials. - : Springer Nature. - 2662-4443. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- LiCrSe2 constitutes a recent valuable addition to the ensemble of two-dimensional triangular lattice antiferromagnets. In this work, we present a comprehensive study of the low temperature nuclear and magnetic structure established in this material. Being subject to a strong magnetoelastic coupling, LiCrSe2 was found to undergo a first order structural transition from a trigonal crystal system (P3 ¯ m1) to a monoclinic one (C2/m) at T s = 30 K. Such restructuring of the lattice is accompanied by a magnetic transition at T N = 30 K. Refinement of the magnetic structure with neutron diffraction data and complementary muon spin rotation analysis reveal the presence of a complex incommensurate magnetic structure with a up-up-down-down arrangement of the chromium moments with ferromagnetic double chains coupled antiferromagnetically. The spin axial vector is also modulated both in direction and modulus, resulting in a spin density wave-like order with periodic suppression of the chromium moment along the chains. This behavior is believed to appear as a result of strong competition between direct exchange antiferromagnetic and superexchange ferromagnetic couplings established between both nearest neighbor and next nearest neighbor Cr3+ ions. We finally conjecture that the resulting magnetic order is stabilized via subtle vacancy/charge order within the lithium layers, potentially causing a mix of two co-existing magnetic phases within the sample.
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| 5. |
- Nocerino, Elisabetta, et al.
(författare)
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The Duel of Magnetic Interactions and Structural Instabilities: Itinerant Frustration in the Triangular Lattice Compound LiCrSe2
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The recent synthesis of the chromium selenide compound LiCrSe2 constitutes a valuable addition to the ensemble of two-dimensional triangular lattice antiferromagnets (2D-TLA). In this work we present the very first comprehensive study of the combined low temperature nuclear and magnetic structure established in this material. Details on the connection between Li-ion dynamics and structural changes are also presented along with a direct link between atomic structure and spin order via a strong magnetoelastic coupling. LiCrSe2 was found to undergo a first order structural transition from a trigonal crystal system with space group P3¯m1 to a monoclinic one with space group C2/m at Ts=30~K. Such restructuring of the lattice is accompanied by a magnetic transition at TN=30~K, with the formation of a complex spin arrangement for the Cr3+ moments. Refinement of the magnetic structure with neutron diffraction data and complementary muon spin rotation analysis reveal the presence of two incommensurate magnetic domains with a up-up-down-down arrangement of the spins with ferromagnetic (FM) double chains coupled antiferromagnetically (AFM). In addition to this unusual arrangement, the spin axial vector is modulated both in direction and modulus, resulting in a spin density wave-like order with periodic suppression of the Cr moment along the chains. This behavior is believed to appear as a result of strong competition between direct exchange AFM and superexchange FM couplings established between both nearest neighbor and next nearest neighbor Cr3+ ions. We finally conjecture that the resulting magnetic order is stabilized via subtle vacancy/charge order within the Li layers, potentially causing a mix of two different magnetic phases within the sample.
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| 6. |
- 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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| 7. |
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| 8. |
- 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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| 9. |
- Witteveen, Catherine, et al.
(författare)
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Synthesis and anisotropic magnetic properties of LiCrTe2 single crystals with a triangular-lattice antiferromagnetic structure
- 2023
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Ingår i: Journal of Physics. - : IOP Publishing. - 2515-7639. ; 6:3
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Tidskriftsartikel (refereegranskat)abstract
- We report on the synthesis of LiCrTe2 single crystals and on their anisotropic magnetic properties. We have obtained these single crystals by employing a Te/Li-flux synthesis method. We find LiCrTe2 to crystallize in a TlCdS2 -type structure with cell parameters of a = 3.9512(5) angstrom and c = 6.6196(7) angstrom at T = 175 K. The content of lithium in these crystals was determined to be neary stoichiometric by means of neutron diffraction. We find a pronounced magnetic transition at T-N(ab) = 144 K and T-N
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