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Liquid Metal Energy Harvester by Acoustic Wave (Vol. 49 No.4)
Application of a temperature gradient to a magnetic medium leads to the generation of a spin current referred to as the longitudinal spin Seebeck effect (LSSE). In a magnetic insulator such a current is created by a flux of thermal magnons. Using spin-dependent electron scattering processes in the adjacent normal metal this current can be converted to an electric voltage. The voltage evolution is determined by the development of the temperature gradient ∇T(x,t) and by the characteristics of the magnon’s motion.
By analysis of the time-dependent LSSE voltages in platinum-coated Yttrium Iron Garnet (YIG) ferrimagnetic films, the authors assumed that thermally-driven magnons with energies above 20 K move through the YIG layer ballistically due to their almost linear quasi-acoustic dispersion law. Consequently, the interaction processes within the ‘acoustic’ magnon mode do not change the magnon propagation velocity, while the number of magnons decays exponentially within an effective propagation length of 425nm. This length was found to be mostly independent on film thickness that proves the ballistic magnon transport scenario.
J. Jeon, S. K. Chung, J.-B. Lee, S. Joo Doo and D. Kim, Acoustic wave-driven oxidized liquid metal-based energy harvester, Eur. Phys. J. Appl. Phys. 81, 20902 (2018)
[Abstract]
Temperature-driven ballistic magnon transport (Vol. 49 No.4)
Application of a temperature gradient to a magnetic medium leads to the generation of a spin current referred to as the longitudinal spin Seebeck effect (LSSE). In a magnetic insulator such a current is created by a flux of thermal magnons. Using spin-dependent electron scattering processes in the adjacent normal metal this current can be converted to an electric voltage. The voltage evolution is determined by the development of the temperature gradient ∇T(x,t) and by the characteristics of the magnon’s motion.
By analysis of the time-dependent LSSE voltages in platinum-coated Yttrium Iron Garnet (YIG) ferrimagnetic films, the authors assumed that thermally-driven magnons with energies above 20 K move through the YIG layer ballistically due to their almost linear quasi-acoustic dispersion law. Consequently, the interaction processes within the ‘acoustic’ magnon mode do not change the magnon propagation velocity, while the number of magnons decays exponentially within an effective propagation length of 425nm. This length was found to be mostly independent on film thickness that proves the ballistic magnon transport scenario.
T. B. Noack and eleven co-authors, Spin Seebeck effect and ballistic transport
of quasi-acoustic magnons in room-temperature yttrium iron garnet films, J. Phys. D: Appl. Phys. 51, 234003 (2018)
[Abstract]
Evidence of Long-range Correlations in Shallow Earthquakes (Vol. 49 No.4)
Earthquakes are one of the most devastating natural disasters by the number of casualties and the negative economic impact. Seismic phenomena have been studied from the viewpoint of complex systems, where complex patterns arise from nonlinear interactions between their elements. One of such ways is using networks of geographical sites; we introduce a new methodology to construct networks of epicenters and applied it to global catalogs of shallow earthquakes. It involves essentially the introduction of a time window, which works as a temporal filter for vertices connections. The resulting network constructed has small-world properties and presents scale-free properties in its connectivity distribution, which we proved to be invariant with respect to the value of the time window adopted. Vertices with larger connectivity in the network correspond to areas with very intense seismic activity in the period considered. These new results constitute evidences of possible spatial and temporal long-range correlations between earthquakes.
D. Ferreira, J. Ribeiro, A. Papa and R. Menezes, Towards evidence of long-range correlations in shallow seismic activities, EPL 121, 58003 (2018)
[Abstract]
The Soreq Applied Research Accelerator Facility (SARAF) (Vol. 49 No.4)
The Soreq Applied Research Accelerator Facility (SARAF) is under construction in the Soreq Nuclear Research Center at Yavne, Israel. Phase I of SARAF (SARAF-I) is already in operation, generating scientific results in several fields of interest, especially the astrophysical s-process. When completed at the beginning of the next decade, SARAF-II will be a user facility for basic and applied nuclear physics, based on a 40 MeV, 5 mA CW proton/deuteron superconducting linear accelerator. This review presents first a technical overview of SARAF-I and II, including a description of the accelerator and its irradiation targets, and provides a survey of existing research programs at SARAF-I. It then describes in some detail the research potential at the completed facility. SARAF-II’s cutting-edge specifications, with its unique liquid lithium target technology, will enable world-competitive research plans in several disciplines: precision studies of beyond-Standard-Model effects by trapping light exotic radioisotopes (including meaningful studies already at SARAF-I); extended nuclear astrophysics research with higher-energy neutrons, including generation and studies of exotic neutron-rich isotopes relevant to the astrophysical r-process; nuclear structure of exotic isotopes; high-energy neutron cross sections for basic nuclear physics and material science research, including neutron-induced radiation damage; neutron-based imaging with an imaging plane flux similar to that of a 5 MW research reactor; accelerator-based neutron therapy; and, last but not least, novel radiopharmaceuticals development and production.
I. Mardor and 28 co-authors, The Soreq Applied Research Accelerator Facility (SARAF): Overview, research programs and future plans, Eur. Phys. J. A 54, 91 (2018)
[Abstract]
