Relations of irreversible intragrain magnetization M and the critical current density Jc for four shapes of grain have been derived directly from the definition of magnetization and the assumption that the Jc in grain be constant (Bean model).

假定晶内临界电流密度 Jc 为常量(Bean 模型),由磁化强度定义直接计算了四种形状的晶粒的不可逆磁化强眨 M 与 Jc 的关系,得到了相应的 Jc(△M)中的几何因子修正量.

In the experimental research, the levitation force of a HTS above a permanent magnetic guideway was first investigated in the case of zero-field cooling. The hysteresis of the levitation force curve and the interaction between a HTS and the applied magnetic field were explained by the Bean model, and the effect of the measuring precess on the levitation force was further analyzed.

3. In magnetic studies, a SQUID magnetometer was used conventionally to determine theinduced current density by the Bean model. The magnetic field and temperature dependence ofcritical current density is determined to fit fully the form of Kramer model, Parameter valuealso are obtained.

3、测量不同磁场(温度)下MgB_2薄膜样品的磁滞回线,结合Bean模型得到临界电流密度与磁场(温度)的关系曲线J_c( T ,B)以及钉扎力的标度行为,拟合J_c( T ,B)曲线以及钉扎力的标度行为,发现与Kramer模型符合。

Magnetic hysteresis loops of different maximum applied fields were measured in LN2 temperature for sintered and melt-textured YBCO superconductors, and the relations between magnetic hysteresis loss, remanent magnetic hysteresis ΔMrem and the maximum applied field Hm were obtained. The results of themelt-textured samples are well coincident with Bean model, but the results of the sintered sample deviate from Bean model.

We have measured the sample's zero-field cooled (ZFC) and the field-cooled (FC) magnetization as functions of temperature at 5mT and studied its hysteresis loop at various thickness.

Based on bean critical state model, the critical current densities in intergrain and intragrain in high temperature granular superconducting ceramics have been determined by ac susceptibility measurements.

The results can be predicted analytically by Norris equations based on the Bean critical state model when the frequency of transport currents is lower.

It is shown that the nature of the critical state in polycrystalline wafers, unlike that in a ceramic wafer, is not described by the Bean model.

It is shown that the evolution of magnetic flux distribution is adequately described in terms of a modified Bean model with time-dependent critical current.

These facts contradict the generally accepted Bean model.

It is shown that solutions like shock waves may arise beyond the applicability domain of the Bean model.

Pinning of planar vortices in a three-dimensional Josephson medium and the applicability of the Bean model

The analysis of the present paper shoows that it is possible to extend theBean Model to study the properties of the nonideal type Ⅱ supereonductor,inmixed state,in the presence of a high frequency(10~5-10~7hz)field,assnmingthat the pinning force is so strong that the energy dissipation of the flux flowresistance can be neglected.The distribution of the magnetic field,the eriticalcurrent and the temperature inside a superconducting plate are calculated.Ourresults show that there exists a critical frequency.so...

The analysis of the present paper shoows that it is possible to extend theBean Model to study the properties of the nonideal type Ⅱ supereonductor,inmixed state,in the presence of a high frequency(10~5-10~7hz)field,assnmingthat the pinning force is so strong that the energy dissipation of the flux flowresistance can be neglected.The distribution of the magnetic field,the eriticalcurrent and the temperature inside a superconducting plate are calculated.Ourresults show that there exists a critical frequency.so long as the frequency ofthe external field is less than it,the superconducting plate,remains in the mixedstate.

Relations of irreversible intragrain magnetization M and the critical current density Jc for four shapes of grain have been derived directly from the definition of magnetization and the assumption that the Jc in grain be constant (Bean model).It is shown that the diamagnetic field and hence demagnetization factor are not important except for Meissner state and the mixed state near Hc1 for type two superconductors For ceramic oxide superconductors with weak links,its intergrain field is nearly the same as the...

Relations of irreversible intragrain magnetization M and the critical current density Jc for four shapes of grain have been derived directly from the definition of magnetization and the assumption that the Jc in grain be constant (Bean model).It is shown that the diamagnetic field and hence demagnetization factor are not important except for Meissner state and the mixed state near Hc1 for type two superconductors For ceramic oxide superconductors with weak links,its intergrain field is nearly the same as the applied one.Influence of the nonsu-perconductive part of the bulk sample on its measured irreversible magnetization M has been discussed as well.

Through varying the temperature gradient and the cooling rate, the factors influencing the properties of the bulk Y-Ba-Cu-O materials fabricated by Melt-Textured Growth method were studied. The X-ray diffraction pattern of the cleavage plane of the sample fabricated under the more ideal conditions shows that the preferentially aligned along the a-b plane. We have measured the sample's zero-field cooled (ZFC) and the field-cooled (FC) magnetization as functions of temperature at 5mT and studied its hysteresis...

Through varying the temperature gradient and the cooling rate, the factors influencing the properties of the bulk Y-Ba-Cu-O materials fabricated by Melt-Textured Growth method were studied. The X-ray diffraction pattern of the cleavage plane of the sample fabricated under the more ideal conditions shows that the preferentially aligned along the a-b plane. We have measured the sample's zero-field cooled (ZFC) and the field-cooled (FC) magnetization as functions of temperature at 5mT and studied its hysteresis loop at various thickness. It has been found that M(M=M+-M-, where M+ and M- are the magnetizations in the increasing and decreasing field process, respectively is proportional to the sample's thickness. This indicates that the Bean critical state is founded in the sample. The critical current density estimated at 77K and 150mT is 6750 A/cm2.