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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 Hf
Ta
Fe 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.
Ding, F.*; Luo, G.-N.*; Pitts, R.*; Litnovsky, A.*; Gong, X.*; Ding, R.*; Mao, H.*; Zhou, H.*; Wampler, W. R.*; Stangeby, P. C.*; et al.
Journal of Nuclear Materials, 455(1-3), p.710 - 716, 2014/12
被引用回数：25 パーセンタイル：88.12(Materials Science, Multidisciplinary)A movable material probe system (Material and Plasma Evaluation System: MAPES) with an independent pumping system and a sample exchange chamber has been developed and installed on a horizontal port of the EAST tokamak for studies of plasma material interaction (PMI). In the 2012 experimental campaign, deposition and erosion were studied for three samples: mock-up of the outer first wall panels (FWPs) in ITER, castellated tungsten, and molybdenum mirrors. The FWPs with carbon deposition layer were exposed to helium plasmas. The maximum erosion rate of the carbon was valuated to be 8 nm/s. The castellated tungsten with rectangular cells and roof-like shaped cells was exposed to deuterium plasmas to compare amount of deposits on the gap surface. The amount of carbon and boron impurities on the gap surface of the roof-like shaped cells were reduced to less than 30% compared with that of the rectangular cells. The molybdenum mirrors of which protective ducts are installed in front were exposed to deuterium plasmas in order to investigate effects of length of the ducts. It was found that the reflectivity of the mirrors with 60 mm-long protective ducts is kept the initial reflectivity.
