A numerical simulation in real space was developed to investigate weak localization corrections to the conductivity in inhomogeneous magnetic fields created by flux lines.Both cylinder model and exponential one of flu...A numerical simulation in real space was developed to investigate weak localization corrections to the conductivity in inhomogeneous magnetic fields created by flux lines.Both cylinder model and exponential one of flux lines were studied.It was shown that the corrections are sensitive to the flux line structure.Comparing to the experiments of Bending et al.,the results show that the flux line in Pb film can be approximately described by the cylinder model.展开更多
Using magnetic decoration technique,the distribution of magnetic flux in power-melting-processed Y-Ba-Cu-O superconductor has been studied in an applied field of 200G at 64K.The decoration patterns indicate that twin ...Using magnetic decoration technique,the distribution of magnetic flux in power-melting-processed Y-Ba-Cu-O superconductor has been studied in an applied field of 200G at 64K.The decoration patterns indicate that twin boundaries act as strong flux pinning sites and the nonsuperconducting Y_(2)BaCuO_(5)(211)inclusions provide pinning sites in their vicinity by inducing lattice distortion.Chain-like vortex distribution,distorted hexagonal flux line lattice and anisotropic vortices have been observed.展开更多
The results of thermopower measurements in a high J_(c) melt-textured growth(MTG)YBa_(2)Cu_(3)O_(7) bulk sample above 80K are reported,its behavior is strongly anisotropic.The small value in c-direction indicates the ...The results of thermopower measurements in a high J_(c) melt-textured growth(MTG)YBa_(2)Cu_(3)O_(7) bulk sample above 80K are reported,its behavior is strongly anisotropic.The small value in c-direction indicates the existence of an imperfection in the alignment of ab-planes and low resistance channels along the c-axis,which may be important for the high Jc value of the sample.Described by a two order tensor,the orientational dependence of thermopower can also be explained.展开更多
The magnetization properties of an YBa_(2)Cu_(3)O_(~7) superconducting ring were measured at about 80K.The critical field of most of weak couplings is readily obtained and is 170e for the material used.The current is ...The magnetization properties of an YBa_(2)Cu_(3)O_(~7) superconducting ring were measured at about 80K.The critical field of most of weak couplings is readily obtained and is 170e for the material used.The current is most likely distributed in the body of the specimen.The magnetization measurement of a ring-shape specimen may be a good method to study the characters of weak couplings in oxides superconductors.展开更多
The dependence of the effective penetration depthλe,on the external magnetic field in a high-Tc superconducter YBa2Cu3O7 has been measured by both dc and ac methods at liquid-nigtrogen temperature.It is found,thatλe...The dependence of the effective penetration depthλe,on the external magnetic field in a high-Tc superconducter YBa2Cu3O7 has been measured by both dc and ac methods at liquid-nigtrogen temperature.It is found,thatλe increases rapidly with increasing external field and is 0.13~0.15mm in macroscopic scale.The Hcl of the specimen,about 800e at 77K here,can be determined more reliably by comparing dcλe with acλe.The difference betweenλedc andλeac,and the jumping ofλedc may indicate the characters of superconducting glass.展开更多
Resistance measurements at between 1.5 to 40K and Magnetoconductance measurements at about 1.5K have been made on l00ÅCu films,and also on Cu films with small amounts of La,Ce additives.The Ce atoms in Cu seem to...Resistance measurements at between 1.5 to 40K and Magnetoconductance measurements at about 1.5K have been made on l00ÅCu films,and also on Cu films with small amounts of La,Ce additives.The Ce atoms in Cu seem to give much stronger spin-orbit scattering than La atoms do.The behaviour of the Cu film with Ce additives is a composite of weak localization and Kondo effect.展开更多
The time dependence of the penetration of a weak ac field into Y-Ba-Cu-O superconductors at various dc fields,0-1500G,was measured at liquid nitrogen temperature.It is found that the signals are very unstable at certa...The time dependence of the penetration of a weak ac field into Y-Ba-Cu-O superconductors at various dc fields,0-1500G,was measured at liquid nitrogen temperature.It is found that the signals are very unstable at certain field regions for some of the samples.We believe that this is a direct evidence of the existence of flux jumps which are characteristic of granular superconductors.展开更多
The near Iznear temperature dependence of the thermopower in magnetic amorphous FeMnB alloys over a wide temperature range-is reported.It is due to the weakened magnetic extra contribution to the thermopower when enou...The near Iznear temperature dependence of the thermopower in magnetic amorphous FeMnB alloys over a wide temperature range-is reported.It is due to the weakened magnetic extra contribution to the thermopower when enough Fe atoms were replaced by Mn whose contribution is opposite to that of the host.In this situation,using a two-component model、as an extreme simpticatzon of the Feber-Zzman theory of liquid metal,it is able to explain the composition dependence of the thermopower.展开更多
The thermoelectric power(TEP)and l/f noise of a series of YBa_(2)Cu_(3)O_(7-δ)/PrBa_(2)Cu_(3)O_(7-δ)(YBCO/PrBCO)superlattice samples have been measured from 80 to 270K.The TEP of the superlattices has large and posi...The thermoelectric power(TEP)and l/f noise of a series of YBa_(2)Cu_(3)O_(7-δ)/PrBa_(2)Cu_(3)O_(7-δ)(YBCO/PrBCO)superlattice samples have been measured from 80 to 270K.The TEP of the superlattices has large and positive values.For samples with thick YBCO layers,it varies linearly with temperature and has a positive slope.The noise power of superlattice samples is about two orders of magnitude lower than that in bulk YBCO film.展开更多
The behavior of magnetoresistance in thin silver films was investigated from 1.8 up to 104 K.Weak localization effect,manifested by negative magnetoresistance,remains until 88 K in magnetic fields below 2T.Experimenta...The behavior of magnetoresistance in thin silver films was investigated from 1.8 up to 104 K.Weak localization effect,manifested by negative magnetoresistance,remains until 88 K in magnetic fields below 2T.Experimental results indicate that weak localization theory for two-dimensional disordercd systems is applicable even when the phase relaxation length L is a few times longer than the elastic mean free path l,provided L is larger than the thickness of films.The obtained phase relaxation timeτobeys 1/T^(2.6) law.展开更多
The thermoelectric power S of a superconducting Bi_(2)Sr_(2)Ca_(2)O_(x) crystal has been measured from 1TK to 290K,and obvious anisotropy has been observed.The values of S in a-b plane are negative and small,and S in ...The thermoelectric power S of a superconducting Bi_(2)Sr_(2)Ca_(2)O_(x) crystal has been measured from 1TK to 290K,and obvious anisotropy has been observed.The values of S in a-b plane are negative and small,and S in c-axis are positive.If the semiconductorlike behavior of R(T)is intrinsic in c direction,supposing the existence of metallic links between Cu-O planes caused by defects in crystal,the behaviors of S(T)and R(T)in c direction of our sample could be understood.展开更多
The thermoelectric power in amorphous(Fe_(1)-_(x)T_(x))_(84)B_(16) alloys,where T stands for V,Nb,Ta and x ranges from 0 to 0.08,is measured in the temperature range 77-350K.The results can be qualitatively understood...The thermoelectric power in amorphous(Fe_(1)-_(x)T_(x))_(84)B_(16) alloys,where T stands for V,Nb,Ta and x ranges from 0 to 0.08,is measured in the temperature range 77-350K.The results can be qualitatively understood using Mott s-d scattering model or Herzer's theory on the assumption of the occurrence of a virtual bound state near Fermi level.The differences between FeVB,FeNbB and FeTaB systems confirm the existence of a period effect in these alloys.展开更多
基金Supported by the National Natural Science Foundation of Chinathe National Fundamental Science Research Program.
文摘A numerical simulation in real space was developed to investigate weak localization corrections to the conductivity in inhomogeneous magnetic fields created by flux lines.Both cylinder model and exponential one of flux lines were studied.It was shown that the corrections are sensitive to the flux line structure.Comparing to the experiments of Bending et al.,the results show that the flux line in Pb film can be approximately described by the cylinder model.
基金Supported by the National Natural Science Foundation of Chinathe Chinese National Center for R&D on Superconductivity.
文摘Using magnetic decoration technique,the distribution of magnetic flux in power-melting-processed Y-Ba-Cu-O superconductor has been studied in an applied field of 200G at 64K.The decoration patterns indicate that twin boundaries act as strong flux pinning sites and the nonsuperconducting Y_(2)BaCuO_(5)(211)inclusions provide pinning sites in their vicinity by inducing lattice distortion.Chain-like vortex distribution,distorted hexagonal flux line lattice and anisotropic vortices have been observed.
基金Supported by the National Centre for Research&Development on Superconductivity.
文摘The results of thermopower measurements in a high J_(c) melt-textured growth(MTG)YBa_(2)Cu_(3)O_(7) bulk sample above 80K are reported,its behavior is strongly anisotropic.The small value in c-direction indicates the existence of an imperfection in the alignment of ab-planes and low resistance channels along the c-axis,which may be important for the high Jc value of the sample.Described by a two order tensor,the orientational dependence of thermopower can also be explained.
基金Project supported by the National Science Foundation of China.
文摘The magnetization properties of an YBa_(2)Cu_(3)O_(~7) superconducting ring were measured at about 80K.The critical field of most of weak couplings is readily obtained and is 170e for the material used.The current is most likely distributed in the body of the specimen.The magnetization measurement of a ring-shape specimen may be a good method to study the characters of weak couplings in oxides superconductors.
基金Project suported by the National Science Fundation of China.
文摘The dependence of the effective penetration depthλe,on the external magnetic field in a high-Tc superconducter YBa2Cu3O7 has been measured by both dc and ac methods at liquid-nigtrogen temperature.It is found,thatλe increases rapidly with increasing external field and is 0.13~0.15mm in macroscopic scale.The Hcl of the specimen,about 800e at 77K here,can be determined more reliably by comparing dcλe with acλe.The difference betweenλedc andλeac,and the jumping ofλedc may indicate the characters of superconducting glass.
文摘Resistance measurements at between 1.5 to 40K and Magnetoconductance measurements at about 1.5K have been made on l00ÅCu films,and also on Cu films with small amounts of La,Ce additives.The Ce atoms in Cu seem to give much stronger spin-orbit scattering than La atoms do.The behaviour of the Cu film with Ce additives is a composite of weak localization and Kondo effect.
基金supported by National Science Foundation of China。
文摘The time dependence of the penetration of a weak ac field into Y-Ba-Cu-O superconductors at various dc fields,0-1500G,was measured at liquid nitrogen temperature.It is found that the signals are very unstable at certain field regions for some of the samples.We believe that this is a direct evidence of the existence of flux jumps which are characteristic of granular superconductors.
基金supported by the Science Fund of the Chinese Academy of Sciences。
文摘The near Iznear temperature dependence of the thermopower in magnetic amorphous FeMnB alloys over a wide temperature range-is reported.It is due to the weakened magnetic extra contribution to the thermopower when enough Fe atoms were replaced by Mn whose contribution is opposite to that of the host.In this situation,using a two-component model、as an extreme simpticatzon of the Feber-Zzman theory of liquid metal,it is able to explain the composition dependence of the thermopower.
基金Supported by the Chinese National Center for Research and Development of Superconductivity,。
文摘The thermoelectric power(TEP)and l/f noise of a series of YBa_(2)Cu_(3)O_(7-δ)/PrBa_(2)Cu_(3)O_(7-δ)(YBCO/PrBCO)superlattice samples have been measured from 80 to 270K.The TEP of the superlattices has large and positive values.For samples with thick YBCO layers,it varies linearly with temperature and has a positive slope.The noise power of superlattice samples is about two orders of magnitude lower than that in bulk YBCO film.
基金Supported by the National Natural Science Foundation of ChinaNational Fuiidanicntai Science Research Program.
文摘The behavior of magnetoresistance in thin silver films was investigated from 1.8 up to 104 K.Weak localization effect,manifested by negative magnetoresistance,remains until 88 K in magnetic fields below 2T.Experimental results indicate that weak localization theory for two-dimensional disordercd systems is applicable even when the phase relaxation length L is a few times longer than the elastic mean free path l,provided L is larger than the thickness of films.The obtained phase relaxation timeτobeys 1/T^(2.6) law.
基金Project supported by Natural Science Fundation of China.
文摘The thermoelectric power S of a superconducting Bi_(2)Sr_(2)Ca_(2)O_(x) crystal has been measured from 1TK to 290K,and obvious anisotropy has been observed.The values of S in a-b plane are negative and small,and S in c-axis are positive.If the semiconductorlike behavior of R(T)is intrinsic in c direction,supposing the existence of metallic links between Cu-O planes caused by defects in crystal,the behaviors of S(T)and R(T)in c direction of our sample could be understood.
基金project supported by the National Science Foundation of China。
文摘The thermoelectric power in amorphous(Fe_(1)-_(x)T_(x))_(84)B_(16) alloys,where T stands for V,Nb,Ta and x ranges from 0 to 0.08,is measured in the temperature range 77-350K.The results can be qualitatively understood using Mott s-d scattering model or Herzer's theory on the assumption of the occurrence of a virtual bound state near Fermi level.The differences between FeVB,FeNbB and FeTaB systems confirm the existence of a period effect in these alloys.
