Dynamic nuclear polarization system for the SANS-J-II spectrometer at JAEA

Kumada, Takayuki; Noda, Yohei; Hashimoto, Takeji; Koizumi, Satoshi

Physica B; Condensed Matter, 404(17), p.2637 - 2639, 2009/09

https://doi.org/10.1016/j.physb.2009.06.050

We have developed dynamic nuclear polarization (DNP) system for SANS-J-II at the JRR-3 atomic research reactor at Japan Atomic Energy Agency. Our system is composed of superconducting magnet (3.3 Tesla), Gunn oscillator as a microwave source (94 GHz), and cryostat (1.2 K). We succeeded in polarizing polyethylene sample up to 0.32 and observing effects of polarization on SANS profile. We plan to use the DNP and SANS system in order to determine structure factors of multi-component systems.

Polarized neutron scattering studies of the Kagom lattice antiferromagnet KFe(OH)(SO)

Matan, K.*; Helton, J. S.*; Grohol, D.*; Nocera, D. G.*; Wakimoto, Shuichi; Kakurai, Kazuhisa; Lee, Y. S.*

Physica B; Condensed Matter, 404(17), p.2529 - 2531, 2009/09

https://doi.org/10.1016/j.physb.2009.06.053

Small-angle neutron scattering study of dynamically polarized polyethylenes

Noda, Yohei; Kumada, Takayuki; Hashimoto, Takeji; Koizumi, Satoshi

Physica B; Condensed Matter, 404(17), p.2572 - 2574, 2009/09

https://doi.org/10.1016/j.physb.2009.06.028

We polarized hydrogen nuclear spins of polyethylene samples, doped with organic radical (TEMPO), by use of a dynamic nuclear polarization (DNP) technique, in which the sample was irradiated by microwave (94 GHz) at 3.3 Tesla and 1.4 K. For the samples under the DNP state, we conducted small-angle scattering experiments with polarized neutrons. For the sample with low crystallinity (polarization: 32%), the shift of the incoherent scattering level was observed. For the sample with high crystallinity (polarization: 23%), the enhancement of the coherent scattering due to the crystalline structure was observed.

Anisotropic spin freezing in lightly-doped LaSrCuO

Matsuda, Masaaki; Fujita, Masaki*; Takeda, Masayasu; Yamada, Kazuyoshi*; Kakurai, Kazuhisa

no journal, , 

Polarized neutron scattering is an important tool to clarify the existence of chirality. Furthermore, it also gives useful information on magnetic anisotropy of the spin fluctuations in the diagonal incommensurate phase. We performed polarized neutron scattering experiments in lightly-doped LaSrCuO. The results showed that the chiral terms are almost negligible, indicating that there is no chirality or that the two chirality domains are equally populated. The diagonal terms originate from the magnetic anisotropy in the antiferromagnetically ordered phase. It was found that the spins lie almost in the CuO plane although a finite out-of-plane component was observed. It was also found that there exists a small anisotropy in the CuO plane and the spin component is larger along the b axis, suggesting the remnant of anisotropy in pure LaCuO.

Polarized small-angle neutron scattering measurements of averaged internal structure in Nd-Fe-B sintered magnets

Takeda, Masayasu; Suzuki, Junichi; Yamaguchi, Daisuke; Akiya, Takahiro*; Kato, Hiroaki*; Sagawa, Masato*; Koyama, Keiichi*

no journal, , 

Nd-Fe-B magnets are now widely used because of the highest BH of them in the commercially available magnets. At the present, Dy, which is one of the rare metals, has to be added to maintain the coercivity especially in the operational temperatures higher than the room temperature. The key to achieve the Dy-free Nd-Fe-B magnets is how to control the grain size and the structure near the grain boundary. We have performed the small-angle neutron scattering (SANS) measurements of the sintered Nd-Fe-B magnets using unpolarized and polarized neutrons to obtain the averaged internal structures of samples with the different coercivity introduced by applying different high magnetic fields during the annealing. We found that inhomogeneity was induced by the magnetic fields applied parallel to . The relation between the inhomogeneity and the coercivity force is unclear at the moment, but we will present possible interpretation.