| 21. |
- Forslund, Ola Kenji, et al.
(författare)
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Magnetic phase diagram of K 2 Cr 8 O 16 clarified by high-pressure muon spin spectroscopy
- 2019
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- The K 2 Cr 8 O 16 compound belongs to a series of quasi-1D compounds with intriguing magnetic properties that are stabilized through a high-pressure synthesis technique. In this study, a muon spin rotation, relaxation and resonance (μ + SR) technique is used to investigate the pressure dependent magnetic properties up to 25 kbar. μ + SR allows for measurements in true zero applied field and hereby access the true intrinsic material properties. As a result, a refined temperature/pressure phase diagram is presented revealing a novel low temperature/high pressure (p C1 = 21 kbar) transition from a ferromagnetic insulating to a high-pressure antiferromagnetic insulator. Finally, the current study also indicates the possible presence of a quantum critical point at p C2 ~ 33 kbar where the magnetic order in K 2 Cr 8 O 16 is expected to be fully suppressed even at T = 0 K.
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| 22. |
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| 23. |
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| 24. |
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| 25. |
- Forslund, Ola Kenji, 1990, et al.
(författare)
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Pressure driven magnetic order in Sr 1 - x Ca x Co 2 P 2
- 2022
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic phase diagram of Sr1-xCaxCo2P2 as a function of hydrostatic pressure and temperature is investigated by means of high pressure muon spin rotation, relaxation and resonance (μ+SR). The weak pressure dependence for the x≠ 1 compounds suggests that the rich phase diagram of Sr1-xCaxCo2P2 as a function of x at ambient pressure may not solely be attributed to chemical pressure effects. The x= 1 compound on the other hand reveals a high pressure dependence, where the long range magnetic order is fully suppressed at pc 2≈ 9.8 kbar, which seem to be a first order transition. In addition, an intermediate phase consisting of magnetic domains is formed above pc 1≈ 8 kbar where they co-exist with a magnetically disordered state. These domains are likely to be ferromagnetic islands (FMI) and consist of an high- (FMI-1) and low-temperature (FMI-2) region, respectively, separated by a phase boundary at Ti≈ 20 K. This kind of co-existence is unusual and is originating from a coupling between lattice and magnetic degrees of freedoms.
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| 26. |
- Forslund, Ola Kenji, et al.
(författare)
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Pressure driven magnetic order in Sr1-xCaxCo2P2
- 2022
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic phase diagram of Sr1-xCaxCo2P2 as a function of hydrostatic pressure and temperature is investigated by means of high pressure muon spin rotation, relaxation and resonance (mu+SR). The weak pressure dependence for the x not equal 1- compounds suggests that the rich phase diagram of Sr1-xCaxCo2P2 as a function of x at ambient pressure may not solely be attributed to chemical pressure effects. The x = 1 compound on the other hand reveals a high pressure dependence, where the long range magnetic order is fully suppressed at p(c2) approximate to 9.8 kbar, which seem to be a first order transition. In addition, an intermediate phase consisting of magnetic domains is formed above p(c1) approximate to 8 kbar where they co-exist with a magnetically disordered state. These domains are likely to be ferromagnetic islands (FMI) and consist of an high- (FMI-(1)) and low-temperature (FMI-(2)) region, respectively, separated by a phase boundary at T-i approximate to 20 K. This kind of co-existence is unusual and is originating from a coupling between lattice and magnetic degrees of freedoms.
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| 27. |
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| 28. |
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| 29. |
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| 30. |
- 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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