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Volumn 80, Issue 2, 2009, Pages

Effect of hole doping on the London penetration depth in Bi2.15 Sr1.85 CaCu2 O8+δ and Bi2.1 Sr1.9 Ca0.85 Y0.15 Cu2 O8+δ

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Indexed keywords


EID: 69649106108     PISSN: 10980121     EISSN: 1550235X     Source Type: Journal    
DOI: 10.1103/PhysRevB.80.024516     Document Type: Article
Times cited : (52)

References (33)
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    • To prevent water-vapor condensing on the samples after the quench, the gold-sample container was placed in a glass beaker and warmed to room temperature by a strong stream of flowing gas. This procedure also worked well for the powder samples that were contained in a gold-foil envelope but typically 1-2 mg were lost each time. All samples were periodically overdoped and remeasured to check that there had been no preferential loss of smaller or larger particles during the quench.
    • To prevent water-vapor condensing on the samples after the quench, the gold-sample container was placed in a glass beaker and warmed to room temperature by a strong stream of flowing gas. This procedure also worked well for the powder samples that were contained in a gold-foil envelope but typically 1-2 mg were lost each time. All samples were periodically overdoped and remeasured to check that there had been no preferential loss of smaller or larger particles during the quench.
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    • S. Barakat, undergraduate summer project, University of Cambridge, 2000, unpublished.
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    • The sequence is composed of four treatments in O2 from 450 to 550°C, then 450°C in O2 (5) and again at step 8. Treatments 6, 7, 9, and 10 correspond to various atmospheres, including vacuum, at temperatures up to 600°C, while 11 represents slow cooling from 450 to 100°C in O2. After the initial heating to 550°C (steps 1-4) the data lie on the same reversible line. When referred to the oxygen content derived from the weight changes (top x axis) this line has a slope of 0.93±0.09.
    • The sequence is composed of four treatments in O2 from 450 to 550°C, then 450°C in O2 (5) and again at step 8. Treatments 6, 7, 9, and 10 correspond to various atmospheres, including vacuum, at temperatures up to 600°C, while 11 represents slow cooling from 450 to 100°C in O2. After the initial heating to 550°C (steps 1-4) the data lie on the same reversible line. When referred to the oxygen content derived from the weight changes (top x axis) this line has a slope of 0.93±0.09.
  • 14
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    • note
    • A commercial (Lake Shore Model DRC-91CA) susceptometer and a homemade one with miniature coils of 2.6 mm internal diameter were used. The former was convenient for absolute magnitude and a wider range of ac fields while the latter could be used down to 1.3 K and gave smoother temperature dependences (absorption of paramagnetic oxygen can give spurious anomalies in magnetic-susceptibility measurements between 40 and 60 K). They were calibrated by measuring pure lead (Pb) spheres at low enough frequencies (3.3 or 33.3 Hz) to have negligible eddy current signals in the normal state. The volume (V) of the powder was found from the weight and x-ray density (6.68 mg/ mm3) and hence the signal (mmax) corresponding to an assembly of perfectly diamagnetic spheres could be found. In our experience the particles settle in the sample capsule so loosely that the magnetic interaction between grains is negligible, but in any case the demagnetization factor of the particles in their holder (the bottom of a gelatin capsule) is approximately 1/3, so the local field acting on any grain will be very close to the applied field.
  • 16
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    • The London equation any diamagnetism arising from current loops that flow out of the ab plane is additive. Since there are two in-plane axes, the appropriate averaging factor for out-of-plane currents and randomly oriented crystallites is 2/3. So for λc r there is an extra diamagnetic signal of 1 4π 1 15 r2 / λc2 emu/ cm3 in the measured susceptibility. With r=1 μm and λc =70 μm, this is only 3× 10-6 emu/ cm3 on the plots of Fig. 2. The effect would be negligible even if λc were a factor of 10 smaller. In our experience λc / λab often follows the behavior of ρc / ρab near 300 K and this only decreases by a factor of 2 between p=0.16 and p=0.20.
    • The London equation 2 B=B/ λ2 is linear, so any diamagnetism arising from current loops that flow out of the ab plane is additive. Since there are two in-plane axes, the appropriate averaging factor for out-of-plane currents and randomly oriented crystallites is 2/3. So for λc r there is an extra diamagnetic signal of 1 4π 1 15 r2 / λc2 emu/ cm3 in the measured susceptibility. With r=1 μm and λc =70 μm, this is only 3× 10-6 emu/ cm3 on the plots of Fig. 2. The effect would be negligible even if λc were a factor of 10 smaller. In our experience λc / λab often follows the behavior of ρc / ρab near 300 K and this only decreases by a factor of 2 between p=0.16 and p=0.20.
  • 20
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    • H. Won and K. Maki, Phys. Rev. B 49, 1397 (1994). 10.1103/PhysRevB.49. 1397
    • (1994) Phys. Rev. B , vol.49 , pp. 1397
    • Won, H.1    Maki, K.2
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    • J. W. Loram, private communication (2009).
    • (2009)
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    • L. Forró, Phys. Lett. A 179, 140 (1993). 10.1016/0375-9601(93) 90664-L
    • (1993) Phys. Lett. A , vol.179 , pp. 140
    • Forró, L.1


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.