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Hysteresis in Transport Critical-Current Measurements of Oxide Superconductors

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ABSTRACT

We have investigated magnetic hysteresis in transport critical-current (Ic) measurements of Ag-matrix (Bi,Pb)2Sr2Ca2Cu3O10–x (Bi-2223) and AgMg-matrix Bi2Sr2CaCu2O8+x (Bi-2212) tapes. The effect of magnetic hysteresis on the measured critical current of high temperature superconductors is a very important consideration for every measurement procedure that involves more than one sweep of magnetic field, changes in field angle, or changes in temperature at a given field. The existence of this hysteresis is well known; however, the implications for a measurement standard or interlaboratory comparisons are often ignored and the measurements are often made in the most expedient way. A key finding is that Ic at a given angle, determined by sweeping the angles in a given magnetic field, can be 17 % different from the Ic determined after the angle was fixed in zero field and the magnet then ramped to the given field. Which value is correct is addressed in the context that the proper sequence of measurement conditions reflects the application conditions. The hysteresis in angle-sweep and temperature-sweep data is related to the hysteresis observed when the field is swept up and down at constant angle and temperature. The necessity of heating a specimen to near its transition temperature to reset it to an initial state between measurements at different angles and temperatures is discussed.

No MeSH data available.


Ic at 0.1 µV/cm versus magnetic field for the Bi-2223 specimen for various field-sweep directions, temperatures, and angles. The order in the legend is the order that these data were taken and the arrows indicate the field-sweep direction: (a) 4 K and 90°, (b) 20 K and 90°, (c) 35 K and 90°, (d) 4 K and 0°, (e) 20 K and 0°, (f) 35 K and 0°.
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f2-j64goo: Ic at 0.1 µV/cm versus magnetic field for the Bi-2223 specimen for various field-sweep directions, temperatures, and angles. The order in the legend is the order that these data were taken and the arrows indicate the field-sweep direction: (a) 4 K and 90°, (b) 20 K and 90°, (c) 35 K and 90°, (d) 4 K and 0°, (e) 20 K and 0°, (f) 35 K and 0°.

Mentions: Many papers [1]–[7] have reported magnetic hysteresis observed in transport critical-current measurements of oxide high-temperature superconductors (HTS). The most common observation of hysteresis is that the measured Ic as a function of H is different when measured with increasing and decreasing field. Thus, Ic(H) is a multi-valued function, as shown in Fig. 2. The measured Ic of an HTS can depend significantly on its history of temperature and applied magnetic-field strength and angle. This phenomenon is referred to as magnetic hysteresis or Ic hysteresis. The effect of Ic hysteresis on the measured Ic can be reset to an initial virgin state by heating the superconductor above its critical temperature Tc. Thus, Ic(T, H, θ) also depends on the history of these parameters.


Hysteresis in Transport Critical-Current Measurements of Oxide Superconductors
Ic at 0.1 µV/cm versus magnetic field for the Bi-2223 specimen for various field-sweep directions, temperatures, and angles. The order in the legend is the order that these data were taken and the arrows indicate the field-sweep direction: (a) 4 K and 90°, (b) 20 K and 90°, (c) 35 K and 90°, (d) 4 K and 0°, (e) 20 K and 0°, (f) 35 K and 0°.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4862823&req=5

f2-j64goo: Ic at 0.1 µV/cm versus magnetic field for the Bi-2223 specimen for various field-sweep directions, temperatures, and angles. The order in the legend is the order that these data were taken and the arrows indicate the field-sweep direction: (a) 4 K and 90°, (b) 20 K and 90°, (c) 35 K and 90°, (d) 4 K and 0°, (e) 20 K and 0°, (f) 35 K and 0°.
Mentions: Many papers [1]–[7] have reported magnetic hysteresis observed in transport critical-current measurements of oxide high-temperature superconductors (HTS). The most common observation of hysteresis is that the measured Ic as a function of H is different when measured with increasing and decreasing field. Thus, Ic(H) is a multi-valued function, as shown in Fig. 2. The measured Ic of an HTS can depend significantly on its history of temperature and applied magnetic-field strength and angle. This phenomenon is referred to as magnetic hysteresis or Ic hysteresis. The effect of Ic hysteresis on the measured Ic can be reset to an initial virgin state by heating the superconductor above its critical temperature Tc. Thus, Ic(T, H, θ) also depends on the history of these parameters.

View Article: PubMed Central - PubMed

ABSTRACT

We have investigated magnetic hysteresis in transport critical-current (Ic) measurements of Ag-matrix (Bi,Pb)2Sr2Ca2Cu3O10–x (Bi-2223) and AgMg-matrix Bi2Sr2CaCu2O8+x (Bi-2212) tapes. The effect of magnetic hysteresis on the measured critical current of high temperature superconductors is a very important consideration for every measurement procedure that involves more than one sweep of magnetic field, changes in field angle, or changes in temperature at a given field. The existence of this hysteresis is well known; however, the implications for a measurement standard or interlaboratory comparisons are often ignored and the measurements are often made in the most expedient way. A key finding is that Ic at a given angle, determined by sweeping the angles in a given magnetic field, can be 17 % different from the Ic determined after the angle was fixed in zero field and the magnet then ramped to the given field. Which value is correct is addressed in the context that the proper sequence of measurement conditions reflects the application conditions. The hysteresis in angle-sweep and temperature-sweep data is related to the hysteresis observed when the field is swept up and down at constant angle and temperature. The necessity of heating a specimen to near its transition temperature to reset it to an initial state between measurements at different angles and temperatures is discussed.

No MeSH data available.