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通过改变磁场与c轴方向夹角测量了熔融织构YBa2Cu3O7- (YBCO)晶体的磁力矩信号响应, 观察到了磁通涡旋系统的锁定(lock-in)转变行为以及锁定转变角正比于外磁场强度的反常现象. 基于Ginzburg-Landau理论和磁通涡旋线Kink结构模型, 对上述锁定转变反常现象进行了分析讨论, 提出了熔融织构YBCO晶体中存在平行于a-b面的延展性关联缺陷结构假设, 导出了锁定转变临界角与温度和磁场之间的关系, 理论分析模型结果与实验测量结果基本符合.
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关键词:
- YBa2Cu3O7-单畴晶体 /
- 磁通涡旋结构 /
- 锁定转变
The magnetization behavior of the layered anisotropic high-Tc superconductor in the mixed state Hc1 H Hc2 has a feature that when the angle between the applied magnetic field H and the CuO plane (a-b plane) is less than a critical value ( L), the vortex lattice is converted from three-dimensional structure into two-dimensional structure, forming a phenomenon so called the lock-in transition, where the flux lines are completely parallel to the a-b plane, and the vertical component of the magnetic induction B丄 (perpendicular to the a-b plane) is consequently zero. So far, there have still existed the differences in the physical explanation of the lock-in phenomenon. For the lock-in phenomenon occurring in the region between the CuO planes, it can be considered to be caused by the transverse Meissner effect. However, for the one occurring in other extended correlated defect areas, such as twin boundaries in YBa2Cu3O7- (YBCO) crystal, this phenomenon is believed to be the results of the energy linearization of the vortices trapped in the defect channels. Many theoretical and experimental studies have revealed the existence of the lock-in behaviors related to the microstructure properties of the superconductor crystals. Therefore, the research of the lock-in transition behavior will be helpful to understand the intrinsic pinning properties of the layered anisotropic superconductors, and the phase transition process in the vortex system. In this paper, we systematically measure the magnetic torque signal in melt texture growth YBCO (MTG-YBCO) bulk and observe an abnormal lock-in transition behavior in the vortex system. The critical angle of the lock-in transition is found to be directly proportional to the strength of the magnetic field, which is contrary to the observations in the common cases. According to the framework of the Ginzburg-Landau theory and the kink structure model of the vortex line, we discuss the abnormal phenomenon, and propose that there is a type of extend-correlated defect structure, which is parallel to the a-b plane, in the MTG-YBCO crystal. The relationship between the critical angle of the lock-in transition to the temperature and the magnetic field is established theoretically, and the theoretical results coincide well with the torque measurements.[1] Tinkham M 1996 Introduction to Superconductivity (New York: Dover Publication, Inc) pp314-383
[2] Blatter G 1994 Rev. Mod. Phys. 66 1285
[3] Farrell D E, Rice J P, Ginsberg D M, Liu J Z 1990 Phys. Rev. Lett. 64 1573
[4] Feinberg D, Villard C 1990 Phys. Rev. Lett. 65 919
[5] Kwok W K, Welp U, Vinokur V M, Fleshler S, Downey J, Crabtree G W 1991 Phys. Rev. Lett. 67 390
[6] Bulaevskii L N 1991 Phys. Rev. B 44 910
[7] Sonin E B 1993 Phys. Rev. B 48 10487
[8] Zhukov A A, Perkins G K, Thomas J V, Caplin A D, Kupfer H, Wolf T 1997 Phys. Rev. B 56 3481
[9] Kogan V G 1988 Phys. Rev. B 38 7049
[10] Vulcanescu V, Collin G, Kojima H, Tanaka I, Fruchter L 1994 Phys. Rev. B 50 4139
[11] Zech D, Rossel C, Lense L, Keller H, Lee S L, Karpinski J 1996 Phys. Rev. B 54 12535
[12] Kohout S, Schneider T, Roos J, Keller H, Sasagawa T, Takagi H 2007 Phys. Rev. B 76 064513
[13] Bosma S, Weyeneth S, Puzniak R, Erb A, Keller H 2012 Phys. Rev. B 86 174502
[14] Babu N H, Jackson K P, Dennis A R, Shi Y H, Mancini C, Durrell J H, Cardwell D A 2012 Supercond. Sci. Technol 25 075012
[15] Tang T W, Wu D J, Wu X D, Xu K X 2015 Physica C 519 159
[16] Murakami M 1992 Melt Processed High-Temperature Superconductors (Singapore: World Scientific) pp101-105
[17] Silhanek A, Civale L, Candia S, Nieva G 1999 Phys. Rev. B 59 13620
[18] Avila M A, Civale L, Silhanek V, Ribeiro R A, Lima O F, Lanza H 2001 Phys. Rev. B 64 144502
[19] Kortyka A, Puzniak R, Wisniewski A, Zehetmayer M, Weber H W, Cai Y Q, Yao X 2010 Supercond. Sci. Technol. 23 065001
[20] Kortyka A, Puzniak R, Wisniewski A, Zehetmayer M, Weber H W, Tang C Y, Yao X, Conder K 2010 Phys. Rev. B 82 054510
[21] de Gennes P G 1966 Superconductivity of Metals and Alloys (New York: Benjamin W A) p227
[22] Blatter G, Feigel'man M V, Geshkenbein V B, Larkin A I, Vinokur V M 1994 Rev. Mod. Phys. 66 1125
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[1] Tinkham M 1996 Introduction to Superconductivity (New York: Dover Publication, Inc) pp314-383
[2] Blatter G 1994 Rev. Mod. Phys. 66 1285
[3] Farrell D E, Rice J P, Ginsberg D M, Liu J Z 1990 Phys. Rev. Lett. 64 1573
[4] Feinberg D, Villard C 1990 Phys. Rev. Lett. 65 919
[5] Kwok W K, Welp U, Vinokur V M, Fleshler S, Downey J, Crabtree G W 1991 Phys. Rev. Lett. 67 390
[6] Bulaevskii L N 1991 Phys. Rev. B 44 910
[7] Sonin E B 1993 Phys. Rev. B 48 10487
[8] Zhukov A A, Perkins G K, Thomas J V, Caplin A D, Kupfer H, Wolf T 1997 Phys. Rev. B 56 3481
[9] Kogan V G 1988 Phys. Rev. B 38 7049
[10] Vulcanescu V, Collin G, Kojima H, Tanaka I, Fruchter L 1994 Phys. Rev. B 50 4139
[11] Zech D, Rossel C, Lense L, Keller H, Lee S L, Karpinski J 1996 Phys. Rev. B 54 12535
[12] Kohout S, Schneider T, Roos J, Keller H, Sasagawa T, Takagi H 2007 Phys. Rev. B 76 064513
[13] Bosma S, Weyeneth S, Puzniak R, Erb A, Keller H 2012 Phys. Rev. B 86 174502
[14] Babu N H, Jackson K P, Dennis A R, Shi Y H, Mancini C, Durrell J H, Cardwell D A 2012 Supercond. Sci. Technol 25 075012
[15] Tang T W, Wu D J, Wu X D, Xu K X 2015 Physica C 519 159
[16] Murakami M 1992 Melt Processed High-Temperature Superconductors (Singapore: World Scientific) pp101-105
[17] Silhanek A, Civale L, Candia S, Nieva G 1999 Phys. Rev. B 59 13620
[18] Avila M A, Civale L, Silhanek V, Ribeiro R A, Lima O F, Lanza H 2001 Phys. Rev. B 64 144502
[19] Kortyka A, Puzniak R, Wisniewski A, Zehetmayer M, Weber H W, Cai Y Q, Yao X 2010 Supercond. Sci. Technol. 23 065001
[20] Kortyka A, Puzniak R, Wisniewski A, Zehetmayer M, Weber H W, Tang C Y, Yao X, Conder K 2010 Phys. Rev. B 82 054510
[21] de Gennes P G 1966 Superconductivity of Metals and Alloys (New York: Benjamin W A) p227
[22] Blatter G, Feigel'man M V, Geshkenbein V B, Larkin A I, Vinokur V M 1994 Rev. Mod. Phys. 66 1125
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