The resistance,ac susceptibility and Hall coefficient measurements were carried out for the high quality single phase Bi_(2)Sr_(2)CaCu_(2)O_(y) samples with different oxygen contents.It is found that the number of ext...The resistance,ac susceptibility and Hall coefficient measurements were carried out for the high quality single phase Bi_(2)Sr_(2)CaCu_(2)O_(y) samples with different oxygen contents.It is found that the number of extra oxygen atoms in the samples can be easily modulated when they are annealed in low vacuum,and that the relationship between T_(c) and P^(+) is unmonotonic with an optimum P^(+)=0.27holes/CuO_(2) plane corresponding to the highest T_(c)(=95K).This unmonotonic relationship is discussed briefly.展开更多
Besides the structure and oxygen content,the resistance-temperature relationship,Hall carrier concentration(nH)and midpoint temperature of superconducting transition(T_(c))were measured for more than six 123-phase sys...Besides the structure and oxygen content,the resistance-temperature relationship,Hall carrier concentration(nH)and midpoint temperature of superconducting transition(T_(c))were measured for more than six 123-phase systems with elemental substitution.No correlation is found between the oxygen content and T_(c),nor is between the orthorhombic structure and T_(c).Instead,an unmonotonic relationship is jound between nH and T_(c).The optimum nH for the highest T_(c) is about 3.8 x1021cm-3.All this draws a conclusion that nH is a parameter to describe the high T_(c) superconductivity.展开更多
The ac magnetic susceptibility,the magnetoresistance R(H)and the dependence of the resistivity on temperature under different applied field were investigated in the Pb-doped Bi-Ca-Sr-Cu-O system.A superconducting phas...The ac magnetic susceptibility,the magnetoresistance R(H)and the dependence of the resistivity on temperature under different applied field were investigated in the Pb-doped Bi-Ca-Sr-Cu-O system.A superconducting phase with Tc-100K exists tn this sintered sample.It forms a well connecting network,and therefore the Josephson coupling between the superconducting grains is sharply improved by doping lead.展开更多
In this paper,the flux pinning effects in Y_(1-x)M_(x)Ba_(2)Cu_(3)O_(7-δ)(M=Gd,Eu and Sm)samples are reported.It is found that there is another pinning mechanism under higher magnetic fields in addition to that under...In this paper,the flux pinning effects in Y_(1-x)M_(x)Ba_(2)Cu_(3)O_(7-δ)(M=Gd,Eu and Sm)samples are reported.It is found that there is another pinning mechanism under higher magnetic fields in addition to that under lower fields.This pinning effect may stem from the lattice stress field resulting from the partial substitution of the rare earth elements with different atomic radii for Y.展开更多
Measurements of the Hall coefficient(RH)were carried out for a polycrystalline YBa_(2)Cu_(3)O_(7-y) film,a well oriented YBa_(2)Cu_(3)O_(7-y) film and an oriented GdBa_(2)Cu_(3)O_(7-y) film.Sign change of RH was obser...Measurements of the Hall coefficient(RH)were carried out for a polycrystalline YBa_(2)Cu_(3)O_(7-y) film,a well oriented YBa_(2)Cu_(3)O_(7-y) film and an oriented GdBa_(2)Cu_(3)O_(7-y) film.Sign change of RH was observed for the two YBa_(2)Cu_(3)O_(7-y) films near Tc,but not for the GdBa_(2)Cu_(3)O_(7-y) film which contains partly the component of(110)orientation.The RH anisotropy model proposed previously turns out to be incorrect.Why the YBa_(2)Cu_(3)O_(7-y) films experience sign change of RH while the GdBa_(2)Cu_(3)O_(7-y) film does not is tentatively investigated.展开更多
Two kinds of single crystal YbBa_(2)Cu_(3)O_(7-y) and ErBa_(2)Cu_(3)O_(7-y) have been grown by the fluxed method.They are orthorhombic structure with space group Pmmm,cell parameters are a=3.88Å,b=3.82Å,c=11...Two kinds of single crystal YbBa_(2)Cu_(3)O_(7-y) and ErBa_(2)Cu_(3)O_(7-y) have been grown by the fluxed method.They are orthorhombic structure with space group Pmmm,cell parameters are a=3.88Å,b=3.82Å,c=11.68Åand their typical size are 3×2×2mm^(3).The superconducting critical temperature is over 90K.Their superconductivity is discussed.展开更多
As is well known, the relatively low critical current density J_c and the serious flux motion limit a variety of applications of high-temperature superconductors (HTSCs). The introduction
We have synthesized polycrystalline samples of Fe1.11(Te1-xSx) and single crystals of Fe1+y(Te0.88S0.12),and characterized their properties.Our results show that the solid solution of S in the Fe1.11Te tetragonal latt...We have synthesized polycrystalline samples of Fe1.11(Te1-xSx) and single crystals of Fe1+y(Te0.88S0.12),and characterized their properties.Our results show that the solid solution of S in the Fe1.11Te tetragonal lattice is limited,~10%.We observed superconductivity at ~8 K in both polycrystalline samples and single crystals.Magnetization measurements reveal that the volume fraction is small for this superconducting phase in both polycrystalline samples as-synthesized and single crystals as-grown.It is found that annealing in air enhances the superconducting fraction;the maximum fraction is almost 100% in the single crystals annealed in air at 300°C.We discuss the effect of annealing on superconductivity and transport properties at the normal state in the Fe1+y(Te1-xSx) system in terms of decrease of the excess Fe.展开更多
文摘The resistance,ac susceptibility and Hall coefficient measurements were carried out for the high quality single phase Bi_(2)Sr_(2)CaCu_(2)O_(y) samples with different oxygen contents.It is found that the number of extra oxygen atoms in the samples can be easily modulated when they are annealed in low vacuum,and that the relationship between T_(c) and P^(+) is unmonotonic with an optimum P^(+)=0.27holes/CuO_(2) plane corresponding to the highest T_(c)(=95K).This unmonotonic relationship is discussed briefly.
基金Supported by the National Natural Science Foundation of China。
文摘Besides the structure and oxygen content,the resistance-temperature relationship,Hall carrier concentration(nH)and midpoint temperature of superconducting transition(T_(c))were measured for more than six 123-phase systems with elemental substitution.No correlation is found between the oxygen content and T_(c),nor is between the orthorhombic structure and T_(c).Instead,an unmonotonic relationship is jound between nH and T_(c).The optimum nH for the highest T_(c) is about 3.8 x1021cm-3.All this draws a conclusion that nH is a parameter to describe the high T_(c) superconductivity.
文摘The ac magnetic susceptibility,the magnetoresistance R(H)and the dependence of the resistivity on temperature under different applied field were investigated in the Pb-doped Bi-Ca-Sr-Cu-O system.A superconducting phase with Tc-100K exists tn this sintered sample.It forms a well connecting network,and therefore the Josephson coupling between the superconducting grains is sharply improved by doping lead.
文摘In this paper,the flux pinning effects in Y_(1-x)M_(x)Ba_(2)Cu_(3)O_(7-δ)(M=Gd,Eu and Sm)samples are reported.It is found that there is another pinning mechanism under higher magnetic fields in addition to that under lower fields.This pinning effect may stem from the lattice stress field resulting from the partial substitution of the rare earth elements with different atomic radii for Y.
基金Supported by the National Natural Science Foundation of China。
文摘Measurements of the Hall coefficient(RH)were carried out for a polycrystalline YBa_(2)Cu_(3)O_(7-y) film,a well oriented YBa_(2)Cu_(3)O_(7-y) film and an oriented GdBa_(2)Cu_(3)O_(7-y) film.Sign change of RH was observed for the two YBa_(2)Cu_(3)O_(7-y) films near Tc,but not for the GdBa_(2)Cu_(3)O_(7-y) film which contains partly the component of(110)orientation.The RH anisotropy model proposed previously turns out to be incorrect.Why the YBa_(2)Cu_(3)O_(7-y) films experience sign change of RH while the GdBa_(2)Cu_(3)O_(7-y) film does not is tentatively investigated.
文摘Two kinds of single crystal YbBa_(2)Cu_(3)O_(7-y) and ErBa_(2)Cu_(3)O_(7-y) have been grown by the fluxed method.They are orthorhombic structure with space group Pmmm,cell parameters are a=3.88Å,b=3.82Å,c=11.68Åand their typical size are 3×2×2mm^(3).The superconducting critical temperature is over 90K.Their superconductivity is discussed.
文摘As is well known, the relatively low critical current density J_c and the serious flux motion limit a variety of applications of high-temperature superconductors (HTSCs). The introduction
基金supported by the National Natural Science Foundation of China (Grant Nos. 10974175 and 10934005)the National Basic Research Program of China (Grant No. 2009CB929104)the PCSIRT of the Ministry of Education of China (Grant No. IRT0754)
文摘We have synthesized polycrystalline samples of Fe1.11(Te1-xSx) and single crystals of Fe1+y(Te0.88S0.12),and characterized their properties.Our results show that the solid solution of S in the Fe1.11Te tetragonal lattice is limited,~10%.We observed superconductivity at ~8 K in both polycrystalline samples and single crystals.Magnetization measurements reveal that the volume fraction is small for this superconducting phase in both polycrystalline samples as-synthesized and single crystals as-grown.It is found that annealing in air enhances the superconducting fraction;the maximum fraction is almost 100% in the single crystals annealed in air at 300°C.We discuss the effect of annealing on superconductivity and transport properties at the normal state in the Fe1+y(Te1-xSx) system in terms of decrease of the excess Fe.
