| Project/Area Number |
06452063
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体物性Ⅱ(磁性・金属・低温)
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| Research Institution | National Laboratory for High Energy Physics |
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Principal Investigator |
IKEDA Hironobu National Laboratory for High Energy Physics, BSF,Prof., ブースター利用施設, 教授 (90013523)
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| Co-Investigator(Kenkyū-buntansha) |
ITOH Shinichi National Laboratory for High Energy Physics, BSF,Research Associate, ブースター利用施設, 助手 (00221771)
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| Project Period (FY) |
1994 – 1995
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| Project Status |
Completed (Fiscal Year 1995)
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| Budget Amount *help |
¥7,000,000 (Direct Cost: ¥7,000,000)
Fiscal Year 1995: ¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1994: ¥4,600,000 (Direct Cost: ¥4,600,000)
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| Keywords | percolation / fractal / newtron scattering / fracton / anomalous diffusion / 冷中性子 / 高エネルギー分解能 |
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| Research Abstract |
A high-resolution inelastic neutron spectrometer equipped with a superconducting magnet has been installed at the pulsed spallation neutron source (KENS) at KEK.For the first experiment using this spectrometer system, we investigated inelastic neutron scattering from diluted Heisenberg antiferromagnetic systems with applied field. Magnetic excitations in finite-size clusters were observed with energy-resolution of 10 mueV.
The anomalous diffusive motions of spins in a near-percolating Ising antiferromagnet, Rb_2Co_<0.6>Mg_<0.4>F_4, have been observed by high energy-resolution neutron inelastic scattering. The scattering function integrated over momentum space in the paramagnetic phase reveals a long-tailed spectrum having the form of E^< -(0.35<plus-minus>0.06) > superimposed on the Lorentzian lineshape, which originates from the normal critical magnetic scattering. This observation of a power-law decay function is a direct measurement of the anomalous diffusion in a system with fractal geometry.
Using neutron inelastic scattering techniques we investigated the magnetic excitations in a diluted Heisenberg antiferromagnet (RbMn_cMg_<1-c>F_3 with c=0.39) close to the percolation threshold of c_p=0.312.No indication of propagating spin waves was observed throughtout the Brillouin zone, but a broad peak superimposed on Ising-cluster excitations was observed. The origin of this broad peak is attributed to the excitation of fractons in a percolating network.
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