Effects of c-axis Correlated Disorders on High Irreversibility Field in NEG123 Bulk

In order to understand a mechanism of the high irreversibility field in (Nd, Eu, Gd)Ba2Cu3Ox bulk, the vortex states were investigated. As a result, we found that the c-axis correlated disorder plays an important role for the achievement of the high irreversibility field. In addition, the small critical exponents s ? 2-4 in the vortex liquid-solid phase transition were observed in high magnetic fields up to 23 T as shown in the figures. This means that the Bose glass state related to such correlated disorder exists in high magnetic fields up to 23 T at least.

IMR, Tohoku University: S. Awaji, N. Isono, K. Watanabe
SRL-ISTEC: M. Muralidhar, N. Koshizuka
Shibaura Inst. Techn. and SRL-ISTEC : M. Murakami

Reference: S. Awaji, N. Isono, K. Watanabe, M. Muralidhar, M. Murakami and N. Koshizuka, “Mechanism of a High Irreversibility Field for (Nd, Eu, Gd)Ba2Cu3O7 Bulk”, IEEE Trans. Appl. Supercnd. 15 (2005) 3786-3789.

高不可逆磁場の機構解明のため,(Nd, Eu, Gd)Ba2Cu3Oxバルク試料に対する磁束状態を調べた.結果として,c軸相関をもつ欠陥が高不可逆磁場の実現に対し重要な働きをしていることが分かった.さらに,図に示したように,磁束液体−固体相転移においての小さい臨界指数s = 2-4が23Tの高磁場まで観測された.このことはc軸相関欠陥に起因したBoseグラス状態が少なくとも23Tの高磁場まで実現していることを意味している.

東北大学金属材料研究所:淡路 智,磯野伸行,渡辺和雄
超電導工学研究所:M. Muralidhar, 腰塚直己