Magnetically measured irreversibility temperatures in superconducting oxides and alloys

Suenaga, M.; Welch, D.O.; Budhani, R. C.

doi:10.1088/0953-2048/5/1s/001

Cited by 67 publications

(17 citation statements)

References 30 publications

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“…In the x-axis the reduced temperature is reported. The IL has been measured by observing the deformation of the response function in the SQUID magnetometer while changing from an irreversible to a reversible behavior, as suggested in [15]. By this procedure, the IL for J c → 0 and therefore the highest H g irr have been measured (the terminology is that of [16]).…”

Section: Resultsmentioning

confidence: 99%

Magnetic characterization of sintered MgB₂samples: effect of substitution or ‘doping’ with Li, Al and Si

Cimberle

Novák²,

Manfrinetti

et al. 2001

Supercond. Sci. Technol.

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Powdered and sintered MgB 2 samples have been characterized through magnetic measurements performed from T = 5 K up to few degrees above the transition temperature of about 39 K. We found that the sintered samples behave as well-connected bodies, showing no trace of granularity. In order to obtain the critical current density value J c the "Critical State Model" has been therefore employed in a straightforward way. With the aim either to decrease the electron mean free path or to increase its J c we have attempted to introduce defects in the MgB 2 structure by different procedures: substitution of Lithium on the Magnesium site and doping of the precursor Boron powders with Aluminum and Silicon. The best result in terms of J c has been achieved by Silicon doping that, moreover, does not significantly affect the transition temperature.2

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Section: Resultsmentioning

confidence: 99%

Magnetic characterization of sintered MgB₂samples: effect of substitution or ‘doping’ with Li, Al and Si

Cimberle

Novák²,

Manfrinetti

et al. 2001

Supercond. Sci. Technol.

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“…All results reported here were found to be scan-length independent for scans less than 4.0 cm. A similar IL seen in vibrating reed experiments on Nb foils [16]-with the sample held stationary in the solenoid-provides additional evidence that this result is not an artifact of the scanning process.Vanishing of the isothermal magnetic hysteresis has also been used to define an IL [15,17]. It has been reported that this method can give different results than the ZFC-FC method [15,20], but this was not seen in measurements on our sample.…”

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confidence: 87%

“…The resistivity ratio was 5.9. Fieldcooled (FC) and zero-field-cooled (ZFC) magnetization measurements were made in fields ranging from 10 to 3000 G. The procedure is well known and has been reported elsewhere [1,5,6,15,17]. The measurements were performed using a Quantum Design SQUID susceptometer with the sample aligned perpendicular to the magnetic field.…”

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confidence: 99%

“…(It has been reported that the FC magnetization of Nb powder can be thermal-history dependent below the irreversibility temperature [18], but no evidence of this was seen in our sample. )In addition, the susceptometer's scan length was limited to 3.0 cm to minimize the effects of moving the sample through a nonuniform field-an experimental problem reported in earlier work using SQUID susceptometers on hysteretic samples [17,19]. (The fractional variation in field over this length is less than 0.0005.)…”

mentioning

confidence: 99%

“…In addition, the susceptometer's scan length was limited to 3.0 cm to minimize the effects of moving the sample through a nonuniform field-an experimental problem reported in earlier work using SQUID susceptometers on hysteretic samples [17,19]. (The fractional variation in field over this length is less than 0.0005.)…”

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Vortex-lattice melting in Nb

1993

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Detailed measurements and analysis of the temperature and magnetic field dependence of the magnetization and the magnetic relaxation of Nh films have been carried out. An irreversibility line has been identified, below which the remanent magnetization was found to decay logarithmically in time. The data were quantitatively compared to predictions of flux creep, vortex glass, and vortex-lattice-melting models. Only the vortex-lattice-melting model self-consistently explained the data.PACS numbers: 74.60.Ge, 74.60.EcThe magnetic-field-temperature (H-T) phase diagram for high-temperature superconductors has been the subject of intense interest. An irreversibility line (IL) and logarithmic decay of the remanent magnetization were first seen in ceramic LaSrCuO [l]. There has since been an ongoing debate over whether they are caused by glassy kinetics [2][3][4], flux creep [5-8], or vortex-lattice melting [9][10][11][12][13]. Although not necessarily expected [14], similar ILs and time-dependent magnetic properties have been observed in conventional type II superconductors [15,16]. While it is not clear that these features have the same origin as their counterparts in high-7V materials-which are highly anisotropic and more heavily influenced by thermal fluctuations-conventional materials offer a simpler platform for the examination of the various models. In this Letter we present the results of detailed measurements and comprehensive analysis of the temperature and magnetic field dependence of the magnetization, and the decay of the remanent magnetization of Nb films. The analysis strongly suggests the irreversibility line in Nb films is a signature of vortex-lattice melting.The sample studied in detail was rf sputtered onto an oxide layer on a Si substrate and had dimensions 5000 Ax2 mmx2 mm. The resistivity ratio was 5.9. Fieldcooled (FC) and zero-field-cooled (ZFC) magnetization measurements were made in fields ranging from 10 to 3000 G. The procedure is well known and has been reported elsewhere [1,5,6,15,17]. The measurements were performed using a Quantum Design SQUID susceptometer with the sample aligned perpendicular to the magnetic field. The temperature control parameters of the susceptometer were adjusted to eliminate temperature overshoot at the sample during the ZFC measurement. To improve the precision of the data, temperature steps were limited to 0.05 K, and 16 scans were averaged at each temperature. A typical temperature sweep took 12 h. T C (H) was determined from the onset of diamagnetism, and T*(//), the irreversibility temperature, was defined as the lowest temperature where the difference between the FC and ZFC magnetizations was less than the standard deviation of the mean of the FC and ZFC measurements. Above r* the magnetization was reversible; below T* only the FC magnetization was thermal-history independent. (It has been reported that the FC magnetization of Nb powder can be thermal-history dependent below the irreversibility temperature [18], but no evidence of this was seen in our sample....

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Oxide Superconductors

Clarke

Däumling

2006

Materials Science and Technology

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Magnetically measured irreversibility temperatures in superconducting oxides and alloys

Cited by 67 publications

References 30 publications

Magnetic characterization of sintered MgB₂samples: effect of substitution or ‘doping’ with Li, Al and Si

Magnetic characterization of sintered MgB₂samples: effect of substitution or ‘doping’ with Li, Al and Si

Vortex-lattice melting in Nb

Oxide Superconductors

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Magnetically measured irreversibility temperatures in superconducting oxides and alloys

Cited by 67 publications

References 30 publications

Magnetic characterization of sintered MgB2samples: effect of substitution or ‘doping’ with Li, Al and Si

Magnetic characterization of sintered MgB2samples: effect of substitution or ‘doping’ with Li, Al and Si

Vortex-lattice melting in Nb

Oxide Superconductors

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Magnetic characterization of sintered MgB₂samples: effect of substitution or ‘doping’ with Li, Al and Si

Magnetic characterization of sintered MgB₂samples: effect of substitution or ‘doping’ with Li, Al and Si