Temperature- and magnetic-field-dependent resistivity of MgB2 sintered at high-temperature and high-pressure condition

Jung, C. U.; Park, Min-Seok; Kang, Won Nam; Kim, Mun-Seog; Lee, S. Y.; Lee, Sung‐Ik

doi:10.1016/s0921-4534(01)00399-9

Cited by 77 publications

(43 citation statements)

References 12 publications

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“…Looking at the temperature dependence of Taking the value σ n =5×10 6 Ω -1 m -1 at T c from the dc resistivity measurements on this sample [42] we find that σ 2 (0)= 5×10 8 Ω -1 m -1 and the zero temperature penetration depth is λ L =160…”

Section: Results and Analysismentioning

confidence: 96%

“…The MgB 2 sample was prepared by high pressure (3 GPa) synthesis using commercial MgB 2 powder as described elsewhere [3,42,43]. The sample was sintered at 950 °C and then quenched to room temperature.…”

Section: Methodsmentioning

confidence: 99%

“…In this paper we report the results from magnetization measurements and microwave surface impedance measurements on a MgB 2 sample sintered at high temperature and high pressure. This sample has been characterized previously in a SEM study and its dc resistivity and Hall coefficient were reported [3,42,43].…”

Section: Introductionmentioning

confidence: 99%

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Magnetization and microwave study of superconductingMgB2

et al. 2002

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We report magnetic field dependent magnetization and microwave impedance measurements on a MgB 2 superconductor prepared by high pressure synthesis. We find that the upper critical field is linearly dependent on temperature near T c and the dc irreversibility field exponent is ~1.4. The microwave data display an excess surface resistance below T c which is neither observed in low T c nor in high temperature superconductors (HTSC). The real part of the complex conductivity, σ 1 , shows a huge maximum below T c and the imaginary part, σ 2 , is linear for temperatures less than 20 K, which can not be simply accounted for by the weak coupling BCS model with an s-wave superconducting order parameter. We speculate that this may be due to the two gaps reported by other studies.Unlike measurements on the high temperature superconducting cuprates, we find no evidence of weak-links in the superconducting state. By inverting the magnetic field dependent impedance data, we find a vortex depinning frequency that decreases with increasing magnetic field and evidence for an anisotropic upper critical magnetic field.

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Section: Results and Analysismentioning

confidence: 96%

Section: Methodsmentioning

confidence: 99%

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Magnetization and microwave study of superconductingMgB2

et al. 2002

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“…1,4,7 In addition, the T c and the J c and its dependence on magnetic field are also sample dependent. This sample dependency has been previously attributed to the synthesis conditions (pressure or thermal history), 8 or to the presence of Mg deficiencies or to the presence of oxygen-related defects. 9 Several methods have been reported to obtain well-connected and dense samples, and high-pressure synthesis seems to be able to produce fully dense bulk MgB 2 with electrical transport properties superior to those of sintered samples.…”

Section: Introductionmentioning

confidence: 90%

Influence of microstructures and crystalline defects on the superconductivity of MgB2

Serquis

Liao

Zhu

et al. 2002

Journal of Applied Physics

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This work studies the influence of microstructures and crystalline defects on the superconductivity of MgB 2 , with the objective to improve its flux pinning. A MgB 2 sample pellet that was hot isostatic pressed (HIPed) was found to have significantly increased critical current density (J c ) at high fields than its un-HIPed counterpart. The HIPed sample had a J c of 10000 A/cm 2 in 50000 Oe (5 T) at 5K. This was 20 times higher than that of the un-HIPed sample, and the same as the best J c reported by other research groups. Microstructures observed in scanning and transmission electron microscopy indicate that the HIP process eliminated porosity present in the MgB 2 pellet resulting in an improved intergrain connectivity. Such improvement in intergrain connectivity was believed to prevent the steep J c drop with magnetic field H that occurred in the un-HIPed MgB 2 pellet at H > 45000 Oe (4.5 T) and T = 5 K. The HIP process was also found to disperse the MgO that existed at the grain boundaries of the un-HIPed MgB 2 pellet and to generate more dislocations in the HIPed the pellets. These dispersed MgO particles and dislocations improved flux pinning also at H<45000 Oe. The HIPing process was also found to lower the resistivity at room temperature.74.70. Ad, 74.60.Ge, 74.62.Bf, 74.25.Fy 1

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“…Recently, effect of sintering temperature 500-950 o C at 3 GPa on the superconducting properties of MgB 2 was studied 6) . It was found that as sintering temperature increased, the sample quality was improved, but for the heat treatment above 950 o C the gold started to melt and to adhere strongly to MgB 2.…”

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Growth, Structure Analysis and Anisotropic Superconducting Properties of MgB₂Single Crystals

et al. 2001

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Here we report the growth of sub-millimeter MgB 2 single crystals of various shapes under high pressure in Mg-B-N system. Structure refinement using a singlecrystal X-ray diffraction analysis gives lattice parameters a=3.0851 (5) . It was found that as sintering temperature increased, the sample quality was improved, but for the heat treatment above 950 o C the gold started to melt and to adhere strongly to MgB 2. Preparation of high-density bulk MgB 2 materials at a higher temperature (950-1250 o C) and 3.5 GPa was reported in BN crucibles 7) . However, the samples prepared at 1250 o C apparently showed inhomogeneous structure in macroscopic scale, indicating the occurrence of contamination from the crucible wall. PACSThese results are not quite favorable for crystal growth of MgB 2 under high-pressure.In this letter, we report the successful growth of high-quality MgB 2 single crystals under high pressure in the Mg-B-N system. Using the crystals, we carried out structure refinement and measured anisotropic superconducting properties of magnesium diboride. were used for refinement after absorption correction by a ψ-scan. The structure was refined by the full-matrix least-square procedure.The temperature dependence of the magnetization M(T) was measured by a SQUID (MPMS XL, Quantum Design) for 37 crystals of different shape (total weight 0.25mg) aligned with the c-axis perpendicular to the sample holder. In-plane electrical resistivity was measured for several plate-like crystals of typical size of 500x100x20 µm 3 in a four-probe configuration using a low frequency (17.8Hz) ac technique with a voltage resolution of less than 0.3nV. To study the anisotropic superconducting properties, the resistivity measurements were performed in the magnetic fields up to 7Tesla applied parallel and perpendicular to the Mg and B planes.The Mg-B-N system has been extensively studied during last 40 years [8][9][10] . In this system Mg and Mg-containing compounds act as the catalysts for the 4 transformation of boron nitride (BN) from hexagonal to cubic form under high pressure and the formation of MgB 2 and MgB 6 crystals has been observed 11). These compounds were formed as the intermediate phases in Mg-BN system, during the synthesis of cubic boron nitride, but MgB 2 was decomposed after prolong heat treatment.We found that the lower limit for MgB 2 crystal growth in "pressure- , using polycrystalline and powdered sample, refined structural data were previously unavailable. It has been proved to be very difficult to avoid the formation of impurity phases (MgO and MgB 4 ) in polycrystalline samples and thus the precise structure refinement is almost impossible. In this study well-formed single crystals were chosen for structure analysis to minimize of absorption effects. The refined crystallographic data, atomic coordinates, and thermal parameters are listed in Table 1 .In the final part of this letter we briefly characterize the superconducting properties of our MgB 2 single crystals. .In Fig.5(a) we present the resistive supe...

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Temperature- and magnetic-field-dependent resistivity of MgB2 sintered at high-temperature and high-pressure condition

Cited by 77 publications

References 12 publications

Magnetization and microwave study of superconductingMgB2

Magnetization and microwave study of superconductingMgB2

Influence of microstructures and crystalline defects on the superconductivity of MgB2

Growth, Structure Analysis and Anisotropic Superconducting Properties of MgB₂Single Crystals

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Temperature- and magnetic-field-dependent resistivity of MgB2 sintered at high-temperature and high-pressure condition

Cited by 77 publications

References 12 publications

Magnetization and microwave study of superconductingMgB2

Magnetization and microwave study of superconductingMgB2

Influence of microstructures and crystalline defects on the superconductivity of MgB2

Growth, Structure Analysis and Anisotropic Superconducting Properties of MgB2Single Crystals

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Product

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Growth, Structure Analysis and Anisotropic Superconducting Properties of MgB₂Single Crystals