1999 Fiscal Year Final Research Report Summary
The Critical Current Density and Pin Potential of High-Tc Oxide Superconductors
| Project/Area Number |
10650313
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | Kumamoto University |
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Principal Investigator |
MIYAHARA Kuniyuki Faculty of Engineering, Kumamoto University, Associate Professor, 工学部, 教授 (90040401)
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| Co-Investigator(Kenkyū-buntansha) |
FUJIYOSHI Takanori Faculty of Engineering, Kumamoto University, Associate Professor, 工学部, 助教授 (80212190)
KUBOTA Hiroshi Faculty of Engineering, Kumamoto University, Associate Professor, 工学部, 助教授 (20170037)
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| Project Period (FY) |
1998 – 1999
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| Keywords | high-T_c superconductor / critical current density / irreversibility line / flux glass / flux liquid / pin potential / percolation / peak effect |
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| Research Abstract |
The current-voltage characteristics of high-T_c superconductors depend complicatedly to temperatures of samples and strength of applied magnetic fields. When the values of currents and voltages are normalized properly, every characteristic curves obtained experimentally are reduced to two primitive curves (scaling) whether the temperature of the sample is higher or not higher than some special temperature (glass-liquid transition temperature T_g). Some researchers consider that this phenomenon is a thermodynamic phase transition of the superconductor from a glass phase to a liquid phase. This interpretation means that the temperature T_g is an intrinsic material constant.
In order to investigate this consideration about the phenomenon, we examined the current-voltage characteristics, i.e. parameters included in the normalization constants of various YBa_2Cu_3O_<7-δ> thin films which contained some kind and amount of pinning centers which were introduced by heavy-ion (Au)-irradiation. Furthermore we investigated the sweep rate dependence of the peak effects of critical currents with respect to the magnetic field.
As the results of these investigation we could interpreted the glass-liquid transition with the use of the interaction between flux lines and pinning centers if the strength of the pinning centers distributes properly. Moreover we indicated that the critical current density of high-T_c superconductors is improved if we can introduce proper distribution of pinning centers.
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