arXiv subjects

Tetsuya Yokoo

Publications and source records attributed to Tetsuya Yokoo.

4 recordsLinked to original sources

arXiv2026

Inelastic neutron scattering study on the AFM uniform spin-1/2 chain compound CuSb2O6

We carried out inelastic neutron scattering experiments on a powdered sample of the antiferromagnetic (AFM) uniform spin-1/2 chain compound CuSb2O6.The magnetic excitations appear in the energy range of 1.8 to 13 meV at 2.5 K below the AFM transition temperature (TN = 8.7 K).The gap value (1.8 meV) is close to that evaluated from the specific heat (1.51 meV). The excitations at 12.5 K (> TN) appear gapless. Thus, the 1.8 meV gap is caused by some anisotropy in spin-wave excitations. The gap excitations are strongest at 0.48 corresponding to a length of 0.66 nm. This result is consistent with the theoretical one that the interaction in a Cu pair with a length of 0.65562 nm (Jab) is strongest. The magnetic excitations can be explained by the AFM uniform XXZ chain with Jab = 6.437 meV and DJab = 0.063 meV. The 1.8 meV gap is caused by the small Ising anisotropy (DJab/Jab = 0.0098).

cond-mat.str-el↗

arXiv2019

Noncoplanar ferrimagnetism and local crystalline-electric-field anisotropy in the quasicrystal approximant Au$_{70}$Si$_{17}$Tb$_{13}$

Neutron scattering experiments have been performed to elucidate magnetic properties of the quasicrystal approximant Au$_{70}$Si$_{17}$Tb$_{13}$, consisting of icosahedral spin clusters in a body-centered-cubic lattice. Bulk magnetic measurements performed on the single crystalline sample unambiguously confirm long-range ordering at $T_{\rm C} = 11.6 \pm 1$ K. In contrast to the simple ferromagnetic response in the bulk measurements, single crystal neutron diffraction confirms a formation of intriguing non-collinear and non-coplanar magnetic order. The magnetic moment direction was found to be nearly tangential to the icosahedral cluster surface in the local mirror plane, which is quite similar to that recently found in the antiferromagnetic quasicrystal approximant Au$_{72}$Al$_{14}$Tb$_{14}$. Inelastic neutron scattering on the powdered sample exhibits a very broad peak centered at $\hbar ω\simeq 4$ meV. The observed inelastic spectrum was explained by the crystalline-electric-field model taking account of the chemical disorder at the fractional Au/Si sites. The resulting averaged anisotropy axis for the crystalline-electric-field ground state is consistent with the ordered moment direction determined in the magnetic structure analysis, confirming that the non-coplanar magnetic order is stabilized by the local uniaxial anisotropy.

cond-mat.mtrl-sci↗

arXiv2017

YUI and HANA: Control and Visualization Programs for HRC in J-PARC

We developed control and visualization programs, YUI and HANA, for High- Resolution Chopper spectrometer (HRC) installed at BL12 in MLF, J-PARC. YUI is a comprehensive program to control DAQ-middleware, the accessories, and sample environment devices. HANA is a program for the data transformation and visualization of inelastic neutron scattering spectra. In this paper, we describe the basic system structures and unique functions of these programs from the viewpoint of users.

physics.ins-det↗

arXiv2017

Spin wave dispersion just above the magnetic order-order transition in the metallic antiferromagnet Mn$_3$Pt

Spin wave dispersion in the metallic antiferromagnet Mn$_3$Pt was investigated just above the order-order transition temperature by using the inelastic neutron scattering technique. The spin wave dispersion at $T = 400$ K along [100], [110] and [111] directions was isotropic within the measurement accuracy. The dispersion was described by $({\hbarω})^2 = c^2q^2 + Δ^2$ with $c = 190$ meV Å and $Δ= 3.3$ meV. Compared with the dispersion at $T = 419$ K previously reported, the result demonstrates a large reduction of the stiffness constant $c$ with increasing temperature. This is similar to that observed in the metallic antiferromagnet FePt$_3$, and is an indication of the itinerancy of the magnetic moments.

cond-mat.mtrl-sci↗