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| 2. |
- Milstead, David A., et al.
(author)
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The active muon shield in the SHiP experiment
- 2017
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In: Journal of Instrumentation. - 1748-0221. ; 12
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Journal article (peer-reviewed)abstract
- The SHiP experiment is designed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. An essential task for the experiment is to keep the Standard Model background level to less than 0.1 event after 2 x 10(20) protons on target. In the beam dump, around 10(11) muons will be produced per second. The muon rate in the spectrometer has to be reduced by at least four orders of magnitude to avoid muon-induced combinatorial background. A novel active muon shield is used to magnetically deflect the muons out of the acceptance of the spectrometer. This paper describes the basic principle of such a shield, its optimization and its performance.
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| 3. |
- Avetisyan, A., et al.
(author)
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Preface
- 2019
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In: APSSE 2019 Actual Problems of System and Software Engineering. - : CEUR-WS. ; , s. 1-2
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Conference paper (peer-reviewed)
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| 4. |
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| 5. |
- Bovo, L., et al.
(author)
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Special temperatures in frustrated ferromagnets
- 2018
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In: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 9:1
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Journal article (peer-reviewed)abstract
- The description and detection of unconventional magnetic states, such as spin liquids, is a recurring topic in condensed matter physics. While much of the efforts have traditionally been directed at geometrically frustrated antiferromagnets, recent studies reveal that systems featuring competing antiferromagnetic and ferromagnetic interactions are also promising candidate materials. We find that this competition leads to the notion of special temperatures, analogous to those of gases, at which the competing interactions balance, and the system is quasi-ideal. Although induced by weak perturbing interactions, these special temperatures are surprisingly high and constitute an accessible experimental diagnostic of eventual order or spin-liquid properties. The well characterised Hamiltonian and extended low-temperature susceptibility measurement of the canonical frustrated ferromagnet Dy2Ti2O7 enables us to formulate both a phenomenological and microscopic theory of special temperatures for magnets. Other members of this class of magnets include kapellasite Cu3Zn(OH)6Cl2 and the spinel GeCo2O4.
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| 6. |
- Jacobsen, Henrik, et al.
(author)
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Spin dynamics of the director state in frustrated hyperkagome systems
- 2021
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In: Physical Review B. - : American Physical Society. - 2469-9969 .- 2469-9950. ; 104:5
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Journal article (peer-reviewed)abstract
- We present an experimental study of the magnetic structure and dynamics of two frustrated hyperkagome compounds, Gd3Ga5O12 and Gd3Al5O12. It has previously been shown that Gd3Ga5O12 exhibits long-range correlations of multipolar directors that are formed from antiferromagnetic spins on loops of ten ions. Using neutron diffraction and reverse Monte Carlo simulations we prove the existence of similar magnetic correlations in Gd3Al5O12, showing the ubiquity of these complex structures in frustrated hyperkagome materials. Using inelastic neutron scattering we shed further light on the director state and the associated low-lying magnetic excitations. In addition, we have measured quasielastic dynamics that show evidence of spin diffusion. Finally, we present AC susceptibility measurements on both Gd3Ga5O12 and Gd3Al5O12, revealing a large difference in the low-frequency dynamics between the two otherwise similar compounds.
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| 7. |
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| 8. |
- Twengström, Mikael, 1990-, et al.
(author)
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LiHoF4 : Cuboidal demagnetizing factor in an Ising ferromagnet
- 2020
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In: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 102:14
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Journal article (peer-reviewed)abstract
- The demagnetizing factor can have an important effect on physical properties, yet its role in determining the behavior of nonellipsoidal samples remains to be fully explored. We present a detailed study of the role of spin symmetry in determining the demagnetizing factor of cuboids, focusing, as a model example, on the Ising dipolar ferromagnet LiHoF4. We distinguish two different functions: the demagnetizing factor as a function of intrinsic susceptibility N(chi) and the demagnetizing factor as a function of temperature N(T). For a given nonellipsoidal sample, the function N(chi) depends only on dipolar terms in the spin Hamiltonian, but apart from in the limits x -> 0 and x -> infinity, it is a different function for different spin symmetries. The function N(T) is less universal, depending on exchange terms and other details of the spin Hamiltonian. We apply a recent theory to calculate these functions for spherical and cuboidal samples of LiHoF4. The theoretical results are compared with N(chi) and N(T) derived from experimental measurements of the magnetic susceptibility of corresponding samples of LiHoF4, both above and below its ferromagnetic transition at T-c = 1.53 K. Close agreement between theory and experiment is demonstrated, showing that the intrinsic susceptibility of LiHoF4 and other strongly magnetic systems can be accurately estimated from measurements on cuboidal samples. Our results further show that for cuboids, and implicitly for any sample shape, N(chi) below the ordering transition takes the value N (infinity). This confirms and extends the scope of earlier observations that the intrinsic susceptibility of ferromagnets remains divergent below the transition, in contradiction to the implications of broken symmetry. We discuss the topological and microscopic origins of this result.
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