Study of low-energy magnetic excitations with high energy-resolution neutron spectroscopy

高能分辨率中子谱低能磁激发研究

• 批准号: 06452063
• 负责人: IKEDA Hironobu
• 金额: $ 4.48万
• 依托单位: National Laboratory for High Energy Physics
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06452063/
• 关键词: percolation; fractal; newtron scattering; fracton; anomalous diffusion; 冷中性子; 高エネルギー分解能

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.

在KEK脉冲中子源（KENS）上安装了一台高分辨率超导磁体非弹性中子谱仪，首次利用该谱仪系统研究了外磁场作用下稀释海森堡反铁磁系统的非弹性中子散射。用能量分辨率为10 μ eV的中子非弹性散射观测到了有限尺寸团簇中的磁激发。用高能量分辨率的中子非弹性散射观测到了近自旋Ising反铁磁体Rb_2Co_Mg_F_4中自旋的反常扩散运动<0.6><0.4>。在顺磁相的动量空间上积分的散射函数揭示了具有叠加在洛伦兹线形上的E^&lt; -（0.35 0.06）&gt;形式的长尾谱<plus-minus>，其源自正常临界磁散射。利用中子非弹性散射技术，我们研究了稀释的Heisenberg反铁磁体（RbMn_cMg_<1-c>F_3，c=0.39）在渗流阈值c_p= 0.312附近的磁激发。在布里渊区没有观察到自旋波的传播。但观察到叠加在伊辛团簇激发上的宽峰。这一宽峰的起源归因于在一个分形网络中的分形子的激发。

项目成果

A.Yazaki, K.Tajima, Y.Todate, S.Tomiyoshi and H.Ikeda: "Neutron paramagnetic scattering from antiferromagnetic RbMnF_3 and Mn_3 Pt using time of flight techniques." J.Pys.Soc.Jpn.63. 748 (1994)

A.Yazaki、K.Tajima、Y.Todate、S.Tomiyoshi 和 H.Ikeda：“使用飞行时间技术进行反铁磁 RbMnF_3 和 Mn_3 Pt 的中子顺磁散射。”

K.Iwasa, M.Nishi, H.Ikeda and J.Suzuki: "Pressure-induced long-range magnetic structure in layred antiferromagnets Rb_2Mn_4 and Cs_2MnF_4" J.Phys.Soc.Jpn.63. 1900 (1994)

K.Iwasa、M.Nishi、H.Ikeda 和 J.Suzuki：“层状反铁磁体 Rb_2Mn_4 和 Cs_2MnF_4 中的压力感应长程磁结构”J.Phys.Soc.Jpn.63。

H.Ikeda, J.A.Fernandez-Baca, R.M.Nicklow, M.Takahashi and K.Iwasa: "Fracton excitations in a diluted Hisenberg antiferromagnet near the percolation threshold : RbMn_<0.39> Mg_<0.61>F_3" J.Phys ; Condens.Matter. 6. 10543 (1994)

H.Ikeda、J.A.Fernandez-Baca、R.M.Nicklow、M.Takahashi 和 K.Iwasa：“稀释的海森堡反铁磁体在渗流阈值附近的分形激发：RbMn_<0.39> Mg_<0.61>F_3”J.Phys；

矢崎昭: "Neutron paramagnetic scattering from antiferromagnetic RbMnF3 and Mn3Pt using time of flight technique" J.Phys.soc.Jpn.63. 748-754 (1994)

Akira Yazaki：“使用飞行时间技术进行反铁磁 RbMnF3 和 Mn3Pt 的中子顺磁散射”J.Phys.soc.Jpn.63 (1994)。

岩佐和晃: "High-resolution inelastic neutron scattering from RbMn_cMg_<1-c>F_3" J. Phys. Soc. Jpn.63. 2862-2865 (1994)

Kazuaki Iwasa：“RbMn_cMg_<1-c>F_3 的高分辨率非弹性中子散射”J. Phys. 63 (1994)。