The specific heat of the recently discovered superconductor MgB_(2) has been measured at temperatures ranging from 4.5 to 80 K.Superconducting anomalyΔC at Tc is clearly observed.The total specific heat in normal sta...The specific heat of the recently discovered superconductor MgB_(2) has been measured at temperatures ranging from 4.5 to 80 K.Superconducting anomalyΔC at Tc is clearly observed.The total specific heat in normal state can be well fitted by electronic and phonon contributions.The Debye temperatureθD is obtained to be 737 K,much larger than other intermetallic superconductors.Normal state electronic specific heat coefficientγis found to be 2.48±0.5 mJ/mol.K^(2) andΔC/γTc is between 1.41 and 2.15.展开更多
The critical current density Jc and n-value have been studied from 40 K to critical temperature for four types of Bi-system 2223 tapes with different sheaths.The experimental results demonstrate that the change of Jc ...The critical current density Jc and n-value have been studied from 40 K to critical temperature for four types of Bi-system 2223 tapes with different sheaths.The experimental results demonstrate that the change of Jc can be divided into three parts and n-value has some decrease with a decrease in temperature.In engineering application,a proper working temperature can be selected to satisfy the practical requirement.Furthermore,the temperature effects on critical stress for Ag-sheath tape was also studied.The results demonstrate that the critical stress does not change monotonously with a decrease in temperature.It increases first,then decreases with the further decrease in temperature.展开更多
We have measured the resistance of some Bi_(2)Sr_(2)CaCu_(2)O_(8) superconducting single crystals along ab plane and the c axis.For some of the single crystals,a resistivity anomaly near the superconducting transition...We have measured the resistance of some Bi_(2)Sr_(2)CaCu_(2)O_(8) superconducting single crystals along ab plane and the c axis.For some of the single crystals,a resistivity anomaly near the superconducting transition temperature is observed in the ab plane.This giant resistance peak is independent of the small driving current(I≤40 mA),and the peak is suppressed and vanished gradually with the increasing applied magnetic field(>100 G).We proposed that the resistance peak is a quasi-reentrant behavior due to the superconducting phase inhomogeneous distribution.展开更多
There are two standpoints to explain the formation of the peak of magnetic susceptibility versus temperature in CeNiSn.One is the presence of the pseudo-gapped density of states(DOS)while the other is the development ...There are two standpoints to explain the formation of the peak of magnetic susceptibility versus temperature in CeNiSn.One is the presence of the pseudo-gapped density of states(DOS)while the other is the development of an antiferromagnetic correlation.To check which one is more reasonable,an experiment is designed on measuring magnetic susceptibility under different magnetic fields.It is found that magnetic field can shift the peak of the magnetic susceptibility to lower temperatures while by calculation the presence of the pseudo-gapped DOS cannot shift the peak,which gives another evidence of the existence of antiferromagnetic correlations and is discussed in the light of some recent theoretical model.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.19825111.
文摘The specific heat of the recently discovered superconductor MgB_(2) has been measured at temperatures ranging from 4.5 to 80 K.Superconducting anomalyΔC at Tc is clearly observed.The total specific heat in normal state can be well fitted by electronic and phonon contributions.The Debye temperatureθD is obtained to be 737 K,much larger than other intermetallic superconductors.Normal state electronic specific heat coefficientγis found to be 2.48±0.5 mJ/mol.K^(2) andΔC/γTc is between 1.41 and 2.15.
基金Supported by the National Natural Science Foundation of China under Grant No.19732001.
文摘The critical current density Jc and n-value have been studied from 40 K to critical temperature for four types of Bi-system 2223 tapes with different sheaths.The experimental results demonstrate that the change of Jc can be divided into three parts and n-value has some decrease with a decrease in temperature.In engineering application,a proper working temperature can be selected to satisfy the practical requirement.Furthermore,the temperature effects on critical stress for Ag-sheath tape was also studied.The results demonstrate that the critical stress does not change monotonously with a decrease in temperature.It increases first,then decreases with the further decrease in temperature.
文摘We have measured the resistance of some Bi_(2)Sr_(2)CaCu_(2)O_(8) superconducting single crystals along ab plane and the c axis.For some of the single crystals,a resistivity anomaly near the superconducting transition temperature is observed in the ab plane.This giant resistance peak is independent of the small driving current(I≤40 mA),and the peak is suppressed and vanished gradually with the increasing applied magnetic field(>100 G).We proposed that the resistance peak is a quasi-reentrant behavior due to the superconducting phase inhomogeneous distribution.
基金Supported by the National Natural Science Foundation of China under Grant No.19274049the National Commission of Science and Technology。
文摘There are two standpoints to explain the formation of the peak of magnetic susceptibility versus temperature in CeNiSn.One is the presence of the pseudo-gapped density of states(DOS)while the other is the development of an antiferromagnetic correlation.To check which one is more reasonable,an experiment is designed on measuring magnetic susceptibility under different magnetic fields.It is found that magnetic field can shift the peak of the magnetic susceptibility to lower temperatures while by calculation the presence of the pseudo-gapped DOS cannot shift the peak,which gives another evidence of the existence of antiferromagnetic correlations and is discussed in the light of some recent theoretical model.
