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Li, B.; Luo, X. H.*; Wang, H.*; Ren, W. J.*; Yano, S.*; Wang, C.-W.*; Gardner, J. S.*; Liss, K.-D.*; Miao, P.*; Lee, S.-H.*; et al.
Physical Review B, 93(22), p.224405_1 - 224405_6, 2016/06
被引用回数:45 パーセンタイル:85.49(Materials Science, Multidisciplinary)Competition between ferromagnetic and antiferromagnetic phases on frustrated lattices in hexagonal Laves phase compound HfTaFe is investigated by using neutron diffraction as a function of temperature and magnetic fields and density-functional-theory calculations. At 325 K, the compound orders into the 120 frustrated antiferromagnetic state with well-reduced magnetic moment and an in-plane lattice contraction simultaneously sets in. With further cooling down, however, the accumulated distortion in turn destabilizes this susceptible frustrated structure. The frustration is completely relieved at 255 K when the first-order transition to the ferromagnetic state takes place, where a colossal negative volumetric thermal expansion, /K, is obtained. Meanwhile, the antiferromagnetic state can be suppressed by few Tesla magnetic fields, which results in a colossal positive magnetostriction. Such delicate competition is attributed to the giant magnetic fluctuation inherent in the frustrated antiferromagnetic state. Therefore, the magnetoelastic instability is approached even under a small perturbation.
Chang, L.-J.; Schweika, W.*; Kao, Y.-J.*; Chou, Y. Z.*; Peron, J.*; Brckel, T.*; Yang, H. C.*; Chen, Y. Y.*; Gardner, J. S.*
Physical Review B, 83(14), p.144413_1 - 144413_7, 2011/04
被引用回数:8 パーセンタイル:36.17(Materials Science, Multidisciplinary)Polycrystalline samples of HoTbTiO (0 2) have been prepared and characterized for their structural and magnetic properties. The parent compounds of this solid solution are the spin ice HoTiO and the spin liquid TbTiO. The results of specific heat, elastic and inelastic neutron scattering measurements suggest that the very strong single-ion effects of HoTiO and TbTiO persist in the HoTbTiO (0 2) solid solution, whereas the Tb-Ho correlations are weak, resulting in small shifts in the energy scales but with no dramatic effect on the bulk properties.
入江 吉郎; Dooling, J.*; Horan, D.*; Kustom, R.*; Middendorf, M.*; Pile, G.*; Bayley, D.*; Cross, G.*; Gardner, I.*; Glover, M.*; et al.
Proceedings of 10th European Particle Accelerator Conference (EPAC 2006) (CD-ROM), p.321 - 323, 2006/00
広帯域で低出力インピーダンス第2高調波空洞が日米英の3か国協力により開発された。低出力インピーダンスの特性は、陽極からグリッド電極へのフィードバックループにより実現される。30オーム以下の出力インピーダンスをもつこのシステムは、周波数2.76.2メガヘルツ,繰返し周波数50ヘルツの条件で大電力試験を行い、安定した高電圧発生(加速間隙あたり12キロボルト)に成功した。英国ラザフォード研究所のISISシンクロトロンにこの装置を適用した場合、精度良いビーム平坦化が可能となり空間電荷力が緩和される。その結果、大強度陽子シンクロトロンにおけるビーム損失の低減に大いに役立つことが期待される。