2007　論文

2007年

1:Room and low temperature direct three-dimensional-strain measurements
　　by neutron diffraction on as-reacted and prebent CuNb/Nb₃Sn wire
Oguro, H; Awaji, S; Nishijima, G; et al.
JOURNAL OF APPLIED PHYSICS 101 10 (2007)103913

Abstract
We measured directly by neutron diffraction the axial and lateral residual strains for the prebent and the as-reacted CuNb/Nb3Sn wires at room temperature and at 7 K, in order to investigate the change of the residual strain with prebending treatment. In the axial direction of the wire, the residual strain was changed with 0.20% to the tensile side when measured at both temperatures, while in the lateral direction, the change was 0.08% and 0.03% to the compressive side for the measurements at RT and 7 K, respectively. From the obtained data, we estimated the deviatoric strain. At 7 K, the value is 0.40% for the as-reacted wires and it reduces to 0.19% when the prebending is applied with a strain epsilon(pb)=0.8%. These results suggest that the reduction of the residual strain in the axial direction as well as in the lateral direction, i.e., of the deviatoric strain is responsible for the observed enhancement in the superconducting properties of the prebent Nb3Sn wires. In addition, we succeeded in the quantitative evaluation of the deviatoric strain dependence of the upper critical field for the practical Nb3Sn wire. This is very important for the understanding of the general axial strain dependence of the superconducting properties.

2:Magnetic properties of MnBi
　　in high magnetic fields and high temperature
Onogi, T; Koyama, K; Watanabe, K
JOURNAL OF THE JAPAN INSTITUTE OF METALS 71, 6 (2007)489-493

Abstract
Magnetization measurements of polycrystalline MnBi were carried out in magnetic fields up to 10 T and in the temperature range from 300 to 773 K, in order to clarify the magnetic properties under high magnetic fields and high temperature. The magnetic phase transition temperature (T-c) at a zero magnetic field is 633 K, which almost linearly increases by 2.3 KT-1 with increasing fields up to 10 T. Furthermore, a metamagnetic transition was observed just above T, indicating that the phase transition is first order. The magnetic entropy change is estimated to be 14 J kg(-1) K-1 for 2 T at T-c using Clausius-Clapayron's equation, which is almost constant for magnetic fields up to 10 T.

3:一次相転移物質MnBiの高温・強磁場磁気特性
小野木哲也、小山佳一、渡辺和雄
日本金属学会誌 71 (2007) 489-493.

Abstract
Magnetization measurements of polycrystalline MnBi were carried out in magnetic fields up to 10 T and in the temperature range from 300 to 773 K, in order to clarify the magnetic properties under high magnetic fields and high temperature. The magnetic phase transition temperature (T_c) at a zero magnetic field is 633 K, which almost linearly increases by 2.3 KT^-1 with increasing fields up to 10 T. Furthermore, a metamagnetic transition was observed just above T_c, indicating that the phase transition is first order. The magnetic entropy change is estimated to be 14 J kg^-1 K^-1 for 2 T at T_c using Clausius-Clapayron's equation, which is almost constant for magnetic fields up to 10 T.