| 1. |
- Ge, Yuqing, 1996, et al.
(författare)
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Confirming the high pressure phase diagram of the Shastry-Sutherland model
- 2023
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 2462:1
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Konferensbidrag (refereegranskat)abstract
- A Muon Spin Rotation (μ + SR) study was conducted to investigate the magnetic properties of SrCu2(BO3)2 (SCBO) as a function of temperature/pressure. Measurements in zero field and transverse field confirm the absence of long range magnetic order at high pressures and low temperatures. These measurements suggest changes in the Cu spin fluctuations characteristics above 21 kbar, consistent with the formation of a plaquette phase as previously suggested by inelastic neutron scattering measurements. SCBO is the only known realisation of the Shatry-Sutherland model, thus the ground state mediating the dimer and antiferromagnetic phase is likekly to be a plaquette state.
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| 2. |
- Benedek, Peter, et al.
(författare)
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Quantifying Diffusion through Interfaces of Lithium-Ion Battery Active Materials
- 2020
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 12:14, s. 16243-16249
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Tidskriftsartikel (refereegranskat)abstract
- Detailed understanding of charge diffusion processes in a lithium-ion battery is crucial to enable its systematic improvement. Experimental investigation of diffusion at the interface between active particles and the electrolyte is challenging but warrants investigation as it can introduce resistances that, for example, limit the charge and discharge rates. Here, we show an approach to study diffusion at interfaces using muon spin spectroscopy. By performing measurements on LiFePO4 platelets with different sizes, we determine how diffusion through the LiFePO4 (010) interface differs from that in the center of the particle (i.e., bulk diffusion). We perform ab initio calculations to aid the understanding of the results and show the relevance of our interfacial diffusion measurement to electrochemical performance through cyclic voltammetry measurements. These results indicate that surface engineering can be used to improve the performance of lithium-ion batteries.
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| 3. |
- Brett, Calvin, et al.
(författare)
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Humidity-Induced Nanoscale Restructuring in PEDOT:PSS and Cellulose Nanofibrils Reinforced Biobased Organic Electronics
- 2021
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Ingår i: Advanced Electronic Materials. - : Wiley. - 2199-160X. ; 7:6, s. 2100137-
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Tidskriftsartikel (refereegranskat)abstract
- In times where research focuses on the use of organic polymers as a base for complex organic electronic applications and improving device efficiencies, degradation is still less intensively addressed in fundamental studies. Hence, advanced neutron scattering methods are applied to investigate a model system for organic electronics composed of the widely used conductive polymer blend poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) together with nanocellulose as flexible reinforcing template material. In particular, the impact of relative humidity (RH) on the nanostructure evolution is studied in detail. The implications are discussed from a device performance point of view and the changing nanostructure is correlated with macroscale physical properties such as conductivity. The first humidification (95% RH) leads to an irreversible decrease of conductivity. After the first humidification cycle, however, the conductivity can be reversibly regained when returning to low humidity values (5% RH), which is important for device manufacturing. This finding can directly contribute to an improved usability of emerging organic electronics in daily live.
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| 4. |
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| 5. |
- Elson, Frank, et al.
(författare)
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TRIM Simulations Tool for μ + Stopping Fraction in Hydrostatic Pressure Cells
- 2023
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 2462:1
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Konferensbidrag (refereegranskat)abstract
- For quantum systems or materials, a common procedure for probing their behaviour is to tune electronic/magnetic properties using external parameters, e.g. temperature, magnetic field or pressure. Pressure application as an external stimuli is a widely used tool, where the sample in question is inserted into a pressure cell providing a hydrostatic pressure condition. Such device causes some practical problems when using in Muon Spin Rotation/Relaxation (μ +SR) experiments as a large proportion of the muons will be implanted in the pressure cell rather than in the sample, resulting in a higher background signal. This issue gets further amplified when the temperature dependent response from the sample is much smaller than that of the pressure cell,which may cause the sample response to be lost in the background and cause difficulties in aligning the sample within the beam. To tackle this issue, we have used pySRIM [1] to construct a practical and helpful simulation tool for calculating muon stopping fractions, specifically for the pressure cell setup at the μE1 beamline using the GPD spectrometer at the Paul Scherrer Institute, with the use of TRIM simulations. The program is used to estimate the number of muon stopping in both the sample and the pressure cell at a given momentum. The simultion tool is programmed into a GUI, making it accessible to user to approximate prior to their experiments at GPD what fractions will belong to the sample and the pressure cell in their fitting procedure.
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| 6. |
- Forslund, Ola Kenji
(författare)
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1D to 3D Magnetism in Quantum Materials: A study by Muons, Neutrons & X-rays
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A collection of works stretching from low- to three-dimensional magnetism are presented, studied mostly through muon spin rotation, relaxation and resonance (µ +SR). The theoretical background of this technique is outlined in Chapter 2, which introduces the subject from the muon particle as an astro[1]nomical particle to how they are produced here on Earth. Given the specific properties of weak particle interactions, previous generations of scientists developed the technique of µ +SR. Special care is taken to explain how the anti-muon interacts with magnetic fields and the resulting behaviour of the anti-muon in a given magnetic field configuration. The fundamental principle of µ +SR is to interpret the resulting muon behaviour in order to unveil microscopic details of the compounds of interest. Other experimental techniques were utilised to confirm the assessment made by µ +SR and to probe different aspects of the compounds being studied. Specifically, neutron and X-ray scattering were performed; the corresponding theoretical background is presented in Chapter 4. Interpretations, conclusions and discussions regarding the studied compounds are presented in Chapter 5. This chapter is divided into four parts depending on the study: one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) magnets and studies related to µ +SR in general. The 1D compounds comprise mostly samples within the Hollandite family, which exhibit quasi-1D chains of transition metal ions. These chains may in certain cases facilitate interactions in a 1D fashion, which is a very interesting feature. In particular, a quantum spin liquid phase is found in one of the compounds, stabilised by a peculiar form of charge ordering occurring at high temperature. Microscopic evidence for the absence of a Peierls transition in a ferromagnetic metal-insulator transition compound is presented as well. The 2D compounds include layer-structured samples in which intralayer interactions are assumed to be dominant. Interestingly, the ground state was found to not be governed only by the intralayer interactions, at least in one of the compounds. Instead, the charge distribution in between the layers seems to have a role to play, as the specific cation ordering determined the ground state. A study in which this distribution is changed to study its effect on the ground state is presented. The 3D magnets considered here exhibit unique interactions available in these compounds. Complicated phases emerge above the transition temperature due to modulation of interactions in space. Finally, a collection of interesting studies related to general µ +SR are included in Chapter 5. These include a study of lithium ion diffusion anisotropy detected for the first time by µ +SR and a semantical discussion related to the term muonium. Other studies not related to this thesis are listed in Articles not included in this thesis. This thesis concludes with Chapter 6, which briefly summarises the work and the resulting outcomes. Most importantly, a smaller discussion on the future of physics is presented, considering its implications for society and science as a whole.
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| 7. |
- Forslund, Ola Kenji, et al.
(författare)
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Co-existence of short- and long-range magnetic order in LaCo2P2
- 2021
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 96:12, s. 125864-
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Tidskriftsartikel (refereegranskat)abstract
- The ferromagnetic (FM) nature of the metallic LaCo2P2 was investigated with the positive muon spin rotation, relaxation and resonance (μ+SR) technique. Transverse and zero field μ+ SR measurements revealed that the compound enters a long range FM ground state at K, consistent with previous studies. Based on the reported FM structure, the internal magnetic field was computed at the muon sites, which were predicted with first principles calculations. The computed result agree well with the experimental data. Moreover, although LaCo2P2 is a paramagnet at higher temperatures T > 160 K, it enters a short range ordered (SRO) magnetic phase for K. Measurements below the vicinity of revealed that the SRO phase co-exists with the long range FM order at temperatures 124 K . Such co-existence is an intrinsic property and may be explained by an interplay between spin and lattice degree of freedoms.
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| 8. |
- Forslund, Ola Kenji, et al.
(författare)
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Intertwined magnetic sublattices in the double perovskite compound LaSrNiReO6
- 2020
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9969 .- 2469-9950. ; 102:14
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Tidskriftsartikel (refereegranskat)abstract
- We report a muon spin rotation (μ+SR) study of the magnetic properties of the double perovskite compound LaSrNiReO6. Using the unique length and time scales of the μ+SR technique, we successfully clarify the magnetic ground state of LaSrNiReO6, which was previously deemed as a spin glass state. Instead, our μ+SR results point toward a long-range dynamically ordered ground state below TC=23 K, for which a static limit is foreseen at T=0. Furthermore, between 23K250 K) state. Our results reveal how two separate yet intertwined magnetic lattices interact within the unique double perovskite structure and the importance of using complementary experimental techniques to obtain a complete understanding of the microscopic magnetic properties of complex materials.
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| 9. |
- 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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| 10. |
- 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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