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CHINESE JOURNAL OF LOW TEMPERATURE PHYSICS

Vol.26   No.1   Feb.,  2004

CONTENTS

 

Study of Magnetic Properties and Ion Size Effect for (La_1-xY_x)_2/3Ca_1/3MnO₃ (0¡Üx¡Ü0.3)

Manganese¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ZHANG YU-FENG,  WANG XIN-YNA,

  CAO GUI-XIN,  LIU YONG-SHENG,  JIN CHAO,  N NISHIMURA,  K MORI,  CAO SHI-XUN,  ZHANG JIN-CANG   (7)

Grain Boundary Effect in the Sol-gel Prepared Polycrystalline Manganites¡­¡­¡­

¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­LI JIAN-QIN  (15)

Effects of Different Ti Content on NbTi Superconductor¡äs Critical Current

Densities¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­XIE BAO-HAI,  WU XIAO-ZU,

 LIU XIANG-HONG,  CHEN ZI-LI,  PU MING-HUA,  LI XIAO-GUANG,  CAO LIE-ZHAO,  ZHOU LIAN  (20)

Crystal Structure and Superconductivity of YBa₂Cu₃O_6+x Oxidized by Electrochemical

 Method¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­GUO JUAN,  CHENG GUO-SHENG,  DONG CHENG (25)

The Pseudogap Behavior in Electro-doped Sm_2-xCe_xCuO₄ Single Crystal¡­¡­¡­¡­¡­¡­

¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­CHAI YI-SHENG,  YANG HONG-SHUN,  LIU JIAN,  YU MIN,  CAO LIE-ZHAO (30)

Inhomogeneity Introduced by Zn Impurity in Doped Cuprates¡­¡­¡­¡­¡­¡­¡­¡­SONG YUN (34)

Research on Strain Effect on Cu-Ni Sheathed MgB₂ Superconducting Tape¡­¡­¡­¡­

¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­FU MIN-YI,  PAN GUO-WEI,

 JIAO ZHENG-KUAN,  DING LI-REN,  ZHANG YONG,  CHEN ZHI-YOU, HAN HAN-MIN,  CHEN JING-LIN  (40)

A Scanning Squid Microscope and Its Applications for Magnetic Field Imaging and

Nondestructive Evaluation¡­ZHANG FENG-HUI,  DING HONG-SHENG,  HE YU-SHENG,  CHEN GENG-HUA,

  HAN SHI-JI,  DONG SHI-YING,  YAN XIAO-MING,  YANG QIAN-SHENG,  CHENG ZHAO-JIA,  JIN DUO (45)

The Influence of Nanometer Mg Powder on Preparing MgB₂ Superconducting Sample

¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­FENG QING-RONG,  CHEN JIN-PING,  XU JU,  WANG YU-HAO,  CHEN XIN (50)

A Preliminary Research of the Magnetic Concentration Device for Scanning

Squid Microscope¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ZHANG FENG-HUI,

 DING HONG-SHENG,  ZHONG CHAO-RONG,  HAN SHI-JI,  DONG SHI-YING,  HE YU-SHENG,  S.I.BONDARENKO  (55)

In Situ Monitoring of the Growth of Complex Oxide Thin Films at High Oxygen

Pressures Using a Three stage Pumping Rheed System¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­

¡­¡­¡­¡­¡­¡­¡­¡­¡­CHEN YING-FEI,  LI JIE,  ZHU XIAO-HONG,  WANG PING,  ZHENG DONG-NING (60)

The Capacitance Equivalent Circuit for Quasi TEM HTS Microstrip and the Basic

Capacitance Model¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­ HUANG HUI-FEN,  MAO JUN-FA  (66)

Studies on Some Problems Related to Pi-ring¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­XIE FEI-XIANG,

  DENG PENG,  LING JIAN,  WANG KE,  MA PING,  WANG SHOU-ZHENG,  WANG FU-REN,  DAI YUAN-DONG  (71)

Study on Conductive Characteristics of ZnO Ceramics Doped Nb₂O₅ at Low

Temperature¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­JI YUAN-MING,  ZHANG JIN-CANG  (75)

Numerical Study on Stability of HTS Coil Under High Pulse Currents¡­¡­¡­¡­¡­¡­

¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­¡­LI YU,  LI XIAO-HANG,  SONG NAI-HAO,  XIAO LI-YE  (80)

 

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(La_1-xY_x)_2/3Ca_1/3MnO₃ (x=0¡«0.3)ÌåϵµÄ´ÅÌØÐÔÓë

ƽ¾ùÏ¡ÍÁÀë×ӳߴçЧӦµÄÑо¿

 

ÕÅÓñ·ï¹  ÍõÐÂÑ๠ ½òᦽ¡²  ²Ü¹ðй

ÁõÓÀÉú¹  ¾´  ³¬¹  Î÷´å¿ËÑå²

É­¿ËµÂ²  ²ÜÊÀÑ«¹  ÕŽð²Ö¹

¹ÉϺ£´óѧÎïÀíϵ£¬ÉϺ£  200436

²¸»É½´óѧ¹¤Ñ§²¿£¬¸»É½930-8555 ÈÕ±¾

 

Ñо¿ÁË(La_1-xY_x)_2/3Ca_1/3MnO₃(0.0¡Üx¡Ü0.3)ÌåϵµÄÌØÐÔ£¬¸ø³öÁË´Åת±äζÈT_cÓëLaλƽ¾ùÀë×ӳߴçÖ®¼äµÄ¹ØÁª.½á¹û±íÃ÷£¬ËæY²ôÔÓŨ¶ÈµÄÔö¼Ó£¬½ðÊô-¾øԵת±ä£¨M-I£©Î¶ÈT_MIÏòµÍÎÂÇøÒƶ¯£¬¶ÔÓ¦µÄ·åÖµµç×èÂʦÑ_pÉý¸ß£¬¶Ôx=0.3ÑùÆ·¶øÑÔ£¬½ÏδÌæ´úÑùÆ·£¨x=0.0£©Ôö·ù´ï8¸öÊýÁ¿¼¶Ö®¶à£¬Ö¸³öÓÉÓÚYµÄ²ôÈë¶øÖÂʹLaλƽ¾ùÀë×Ӱ뾶(<r_A>)¼õÉÙÒÔ¼°¾ÖÓò¾§¸ñ½á¹¹»û±äÒýÆðµÄ.´ÅÐÔ²âÁ¿±íÃ÷ÁËÔÚx>0.1µÄ¸ßŨ¶ÈÇøÓò£¬Ëæ×ÅxµÄÔö¼Ó£¬·´Ìú´ÅÐÔÏ໥×÷ÓÃÖð½¥ÔöÇ¿£¬µ¼ÖÂx=0.2ºÍx=0.3µÄÑùÆ·ÔÚ35K×óÓÒ³öÏÖÁË×ÔÐý²£Á§Ì¬.

 

¹Ø¼ü´Ê£º(La_1-xY_x)_2/3Ca_1/3MnO₃ÃÌÑõ»¯Î ´ÅÌØÐÔ£¬ Àë×ӳߴçЧӦ

PACC:   7550L, 7130, 7530

 

 

 

 

STUDY OF MAGNETIC PROPERTIES

AND ION SIZE EFFECT FOR

(La_1-xY_x)_2/3Ca_1/3MnO₃(0¡Üx¡Ü0.3) MANGANESE

 

ZHANG YU-FENG¹    WANG XIN-YNA¹    CAO GUI-XIN¹   LIU YONG-SHENG¹

JIN CHAO¹   N NISHIMURA²   K MORI²   CAO SHI-XUN¹   ZHANG JIN-CANG¹

¹Department of Physics, Shanghai University, Shanghai  200436

²Faculty of Engineering, Toyama University, Toyama 930-8555, Japan

(Received 25 July, 2003; revised manuscript received 15 September, 2003)

 

The magnetic properties of perovskite (La_1-xY_x)_2/3Ca_1/3MnO₃ (0¡Üx¡Ü0.3) compounds are systematically investigated and it is given that the transition temperature T_c is related to average ion size of

 La site. It is found that with the increasing of Y³⁺ doped content, the metal-insulator transition temperature T_MI (M-I) shifts to lower temperature. While the relevant resistance peak¦Ñ_p sharply increases, for the sample of x=0.3, it has enhanced eight orders of magnitudes larger than the non-doped samples (x=0.0). The decrease of average ion size of La site and the local distortion of lattice constant due to the introduction of Y can explain the experimental results. At high concentration area, say when x>0.1, magnetic studies show a gradual increase of antiferromagnetic interaction with

 the increase of x, ultimately leading to a spin-glass-like state for x=0.2 and x=0.3 compounds at about 35K.

 

Keywords: (La_1-xY_x)_2/3Ca_1/3MnO₃ perovsksite manganese£¬magnetic properties£¬ion size effect

PACC:     7550L, 7130, 7530V

 

 

 

Èܽº-Äý½º·¨ÖƱ¸µÄMn»ù¸ÆîÑ¿ó

¶à¾§ÑùÆ·ÖеĿÅÁ£±ß½çЧӦ

 

ÀÇà

Î人Àí¹¤´óѧÎïÀíϵ£¬ Î人  430070

 

Èܽº-Äý½º·¨ÖƱ¸µÄLa_1-xY_x)_2/3Ca_1/3MnO₃¶à¾§ÑùÆ·Á㳡Ϲ۲⵽µÄµç×èËæζȵı仯ͬ×î½üÕë¶ÔÌú´Å½ðÊô¿ÅÁ£Ìå¶øÌá³öµÄÄ£ÐͽøÐÐÁ˶¨Á¿µÄ±È½ÏÐÔÑо¿£¬»ùÓÚÕâÒ»Ñо¿£¬ Mn»ù¸ÆîÑ¿ó¶à¾§ÑùÆ·ÖпÅÁ£±ß½çЧӦµÃÒÔÌÖÂÛ.

 

¹Ø¼ü´Ê£º¿ÅÁ£±ß½ç£¬ ×ÔÐý¼«»¯ËíµÀ£¬ µç×ÓÊäÔ˪¤

PACC£º  7530V£¬ 7340R£¬ 7570C

 

 

GRAIN BOUNDARY EFFECT IN THE SOL-GEL

PREPARED POLYCRYSTALLINE MANGANITES

 

LI JIAN-QIN

Department of Physics, Wuhan University of Technology, Wuhan  430070

 

The temperature dependence of resistivity obtained in the sol-gel prepared polycrystalline La_2/3Ca_1/3MnO₃ samples is quantitatively studied in terms of a model recently proposed for ferromagnetic metallic granular systems. From this study, the grain boundary effect on the electrical transport is discussed for polycrystalline manganites.

 

Keywords: grain boundary, spin-polarized tunneling, electronic transport

PACC:     7530V, 7340R, 7570C

 

 

 

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²»Í¬Tiº¬Á¿¶ÔNbTi³¬µ¼ÌåÁÙ½çµçÁ÷ÃܶȵÄÓ°Ïì

 

 

뱦º£^1,2    ÎâÏþ×æ²   ÁõÏòºê²    ³Â×ÔÁ¦²

ÆÑÃ÷»ª²    ÀîÏþ¹â³    ²ÜÁÒÕ׳    ÖÜ  Á®²

¹¶«±±´óѧ£¬ ÉòÑô  110004

²Î÷±±ÓÐÉ«½ðÊôÑо¿Ôº£¬ Î÷°² 710016

³Öйú¿Æѧ¼¼Êõ´óѧ£¬ ºÏ·Ê  230026

 

ÀûÓÃNbƬºÍTiƬ½»Ìæ×éÅä¼Ó¹¤£¬¾­À©É¢·´Ó¦ÖƱ¸ÁËTiº¬Á¿´Ó43WT%µ½57WT%Ö®¼äµÄÈýÖÖ²»Í¬³É·ÝµÄNbTi³¬µ¼Ïß.²âÁ¿ÁËÈýÖÖ²»Í¬³É·ÝµÄÁÙ½çµçÁ÷ÃܶÈJ_c£¬ÌÖÂÛÁËÔڴų¡Ï²»Í¬Tiº¬Á¿¶ÔNbTiÏßÁÙ½çµçÁ÷ÃܶÈJ_cµÄÓ°Ï죬²¢¶Ô´Åͨ¶¤Ôú»úÖƽøÐÐÁË·ÖÎö.ͨ¹ýɨÃèµç¾µ£¨SEM£©¹Û²ìÁËNb/Ti½çÃæÀ©É¢ÐÎ̬¼°Î¢½á¹¹£¬²¢ÔËÓöàÔ´±ê¶È·ÖÎö·¨^[1]¶Ô²»Í¬³É·ÝµÄNbTi³¬µ¼Ïß½øÐÐÁË´Åͨ¶¤ÔúÁ¦ÃܶÈËæ´Å³¡±ä»¯ÇúÏßµÄÄâºÏ.½á¹û±íÃ÷£ºËæן¬TiÁ¿µÄÔö¼Ó£¬ÆäÁÙ½çµçÁ÷ÃܶÈÔڵͳ¡Ê±ºÜ¸ß£¬¶øÔڸ߳¡Ê±µÄÐÔÄÜÆ«µÍ£¬ÇÒϽµÑ¸ËÙ£¬¶øº¬TiÁ¿µÍµÄ³¬µ¼ÏßÔڸ߳¡Ê±µÄÐÔÄܸü¾ßÓÐÓÅÊÆ£»³¬µ¼ÏßÔÚ²»Í¬´Å³¡ÏµÄÐÔÄÜÊÇÓɵ㶤ÔúºÍÃ涤ÔúÁ½ÖÖ¶¤Ôú»úÖƹ²Í¬×÷Óþö¶¨µÄ.

 

¹Ø¼ü´Ê£ºNbTi³¬µ¼Ìå, ÁÙ½çµçÁ÷ÃܶÈ, ´Åͨ¶¤Ôú

PACC:   7470L, 7460M

 

 

 

EFFECTS OF DIFFERENT Ti CONTENT ON NbTi

SUPERCONDUCTOR¡äS CRITICAL CURRENT DENSITIES

 

XIE BAO-HAI1²  WU XIAO-ZU²  LIU XIANG-HONG²  CHEN ZI-LI²

PU MING-HUA²  LI XIAO-GUANG³  CAO LIE-ZHAO³  ZHOU LIAN²

¹Northeastern University, Shenyang  110004

²Northwest Institute for Nonferrous Metal Research, Xi¡äan  710016

³University of Science and Technology of China, Hefei  230026

 

Three different compositions of NbTi wires have been fabricated by using alternately niobium sheets and titanium sheets. The Ti content may vary from 43WT% to 57WT% by adjusting the relative thickness of the Nb and Ti sheets in the monofilaments. The effects of different Ti content on NbTi superconductor¡äs critical current densities and flux pinning mechanism were discussed. The Nb/Ti interface microstructure and cross-sectional morphology diffusion have been investigated by scanning electron microscopy (SEM). The curve of F_p¡ØB at different composition have been fitted. The results show that the critical current density (J_c) can be improved with higher Ti content in the low field rang(<5T), but the property was weak and rapidly fall in the high field. There are two kinds of flux pinning mechanism dot pinning and subface pinning affect the property in different field.

 

Keywords: NbTi superconductor, critical current densities (J_c), flux pinning

PACC:     7470L, 7460M

 

 

 

  

 

µç»¯Ñ§Ñõ»¯YBa₂Cu₃O_6+xµÄ¾§Ìå½á¹¹ºÍ³¬µ¼µçÐÔÑо¿

 

¹ù  ¾ê^1£¬2   ³Ì¹úÉú^1£¬2£¬3   ¶­  ³É¹

¹Öйú¿ÆѧԺÎïÀíÑо¿Ëù³¬µ¼¹ú¼ÒÖصãʵÑéÊÒ£¬ ±±¾©  100080

²ºÓÄÏʦ·¶´óѧÎïÀíÓëÐÅÏ¢¹¤³ÌѧԺ£¬ ÐÂÏç  453002

³ÄϾ©ÆøÏóѧԺÎïÀíϵ£¬ ÄϾ©  210044

 

ÔڽϵÍζÈÏÂÓõ绯ѧ·½·¨¿ØÖÆYBCO¿é²ÄµÄÑõº¬Á¿¶ÔÉîÈ뿼²ìÆäÑõº¬Á¿¡¢¾§Ìå½á¹¹ºÍ³¬µ¼µçÐÔÖ®¼äµÄ¹ØϵÓÐÖØÒªÒâÒå.ÎÒÃÇÓùÌ̬·´Ó¦·¨ºÏ³É²¢ÓöèÐÔÆøÌåÍË»ð´¦ÀíÖƱ¸³ö·Ç³¬µ¼µÄËÄ·½ÏàYBa₂Cu₃O_6+x£¨x¡«0.1£©¿é²ÄÑùÆ·£¬È»ºóÓÃÈÛÈÚµÄKNO₃NaNO₃×÷Ϊµç½âÖÊ£¬ÓÃYBa₂Cu₃O_6+x¿é²Ä×÷ΪÑô¼«¶ÔÆä½øÐе绯ѧÑõ»¯.Ñô¼«Ñõ»¯ÓúãÁ÷·¨ÔÚ360¡æ½øÐÐ.Ñõ»¯²úÎïµÄµç×è¡¢´Å»¯ÂʺͽṹÌØÐÔ·Ö±ðÓÃËÄÒýÏß·¨¡¢SQUID´ÅÇ¿¼ÆºÍXRD½øÐвⶨ.Ëæ×ÅÑõ»¯Ê±¼äºÍͨ¹ýÑùÆ·µÄµçÁ¿£¨Q£©µÄÔö¼Ó£¬ÑùÆ·Öеij¬µ¼ÏຬÁ¿Öð½¥Ôö¼Ó£¬ÒÀ´Î¿ÉÒÔ»ñµÃ³¬µ¼ÏàÊÇ60KÏàΪÖ÷¡¢60KºÍ90KÁ½Ï๲´æºÍ90Kµ¥ÏàµÄÑùÆ·.XRD·ÖÎöÖ¤Ã÷Á˵绯ѧÑõ»¯ºóÑùÆ·±íÃæºÍÄÚ²¿µÄ½á¹¹²»Í¬£¬±íÃ÷ÁËÑõ·Ö²¼µÄ²»

¾ùÔÈÐÔ£¬ÑùÆ·±í²ãµÄÑõº¬Á¿´óÓÚÄÚ²¿µÄÑõº¬Á¿.

 

¹Ø¼ü´Ê£ºµç»¯Ñ§Ñõ»¯£¬ YBCO£¬ ¾§Ìå½á¹¹£¬ ³¬µ¼µçÐÔ

PACC£º  7470V£¬ 8280F£¬ 6110

 

 

 

 

CRYSTAL STRUCTURE AND SUPERCONDUCTIVITY OF YBa₂Cu₃O_6+x

OXIDIZED BY ELECTROCHEMICAL METHOD

 

GUO JUAN^1,2   CHENG GUO-SHENG^1,2,3    DONG CHENG¹

¹National Lab. for Superconductivity, Institute of Physics, Chinese Academy of Sciences, Beijing  100080

²Department of Physics, Henan Normal University, Xinxiang  453002

³Department of Physics, Nanjing Institute of Meteorology  210044

(Received 10 April, 2003)

 

The electrochemical oxidation was performed on oxygen deficient YBa₂Cu₃O_6+x (x¡«0.1) bulk samples prepared by solid-state method. The oxidation on anode was carried out in molten KNO_3-NaNO₃ at 360¡æ. The samples oxidized electrochemically were characterized by resistance, magnetic susceptibility measurements and XRD analysis. The superconducting volume fraction increases with oxidation time and charge passed through samples. Using this method, we can obtain samples with single superconducting 60K phase or 90K phase and samples containing these two phases. The results of XRD analysis reveal that the structure of outer layer and inter layer is different indicating that the distribution of oxygen in samples is inhomogeneous.

 

Keywords: electrochemical oxidation, YBCO, crystal structure, superconductivity

PACC:     7470V, 8280F, 6110

 

 

 

Sm_2-xCe_xCuO₄µ¥¾§µÄØÍÄÜ϶ÐÐΪÑо¿

²ñÒ»êÉ  Ñîºê˳  Áõ  ½£  Óà  •F  ²ÜÁÒÕ×

Öйú¿Æѧ¼¼Êõ´óѧÎïÀíϵ, ½á¹¹·ÖÎö¿ª·ÅʵÑéÊÒ£¬ºÏ·Ê  230026

 

ÎÒÃÇÔÚµç×ÓÐͳ¬µ¼ÌåSm_1.85Ce_0.15CuO₄ÖÐÊ״ι۲쵽ØÍÄÜ϶µÄÖ¤¾Ý.Ñо¿ÁËÔÚO₂Öв»Í¬ÍË»ðʱ¼ä,µ¥¾§Sm_1.85Ce_0.15CuO₄ÑùÆ·µÄµç×èÂʦѺÍÈȵçÊÆS£¬µç×èÂʦѵIJâÁ¿½á¹ûÏÔʾÍË»ðºóÑùÆ·¸ßÎÂÇøµç×èÂʦѡ¢d¦Ñ/dTºÍÈȵçÊƵÄбÂÊdS/dTбÂÊÔö¼Ó£¬Òâζ×ÅÔØÁ÷×ÓŨ¶ÈϽµ£¬Óë¼õСCe²ôÔÓÁ¿xµÄ×÷ÓõÈЧ.ËùÓеÄÑùÆ·S¡«TºÍ¦Ñ¡«TÇúÏßÔÚij¸öζÈT^*¶¼·¢ÉúбÂʵĸı䣬¸Ãת±äζÈËæ×ÅÍË»ðʱ¼äµÄÔö¼Ó¶øÏò¸ßÎÂÇøÒƶ¯£¬¶øÇÒÔ½À´Ô½Ã÷ÏÔ.Õâ¿ÉÄÜÊÇÒòΪ¸ÃζÈÏÂØÍÄÜ϶±»´ò¿ª£¬ÈȵçÊÆÇúÏßÔÚij¸öζÈÏ´æÔÚÒ»¸ö×îСֵ£¬ÕâÊÇÔØÁ÷×Ó¾ÖÓò»¯µÄ±íÏÖ£»ÈȵçÊÆÇúÏßÉÏ50K¸½½ü¹Û²ìµ½Ò»¸öÃ÷ÏÔµÄÉù×ÓÒ·Òý·å£¬ÕýµÄ·åÖµ±íʾÔØÁ÷×Ó·ûºÅÔÚµÍÎÂÇø·¢ÉúÁ˸ı䣬¼´Óɸßεĵç×ÓÐͱäΪµÍεĿÕѨÐÍ£¬Óë»ô¶ûϵÊýʵÑéÖÐбÂʱ仯һÖÂ.

 

¹Ø¼ü´Ê£ºµç×ÓÐͳ¬µ¼Ì壬 ÊäÔËÐÔÖÊ£¬ ÈȵçÊÆ

PACC:   7470V, 7430F, 7430J

 

 

 

THE PSEUDOGAP BEHAVIOR IN

ELECTRO-DOPED Sm_2-xCe_xCuO₄ SINGLE CRYSTAL

 

CHAI YI-SHENG   YANG HONG-SHUN   LIU JIAN   YU MIN   CAO LIE-ZHAO

Structrual Research lab, Physics Department, University of Science and Technology

y of China, Hefei, Anhui  230026

(Received 10 April, 2003)

 

The pseudogap-like behavior has been observed in electro-doped superconductor Sm_1.85Ce_0.15CuO₄ for the first time. The resistivity ¦Ñ and thermopower S of single crystal Sm_1.85Ce_0.15CuO₄ with different annealing times were measured. The data of temperature dependence of resistivity indicate that the high temperature resistivity ¦Ñ, d¦Ñ/dT and the slope of thermopower dS/dT increase with increasing annealing time, which presume a decrease of charge density and act as the decrease of Ce content

x. In each annealing procedure, the curve of S¡«T and ¦Ñ¡«T change their slopes below a certain temperature T^*. It moves to high temperature region with increase annealing time, and becomes more and more clear, indicating the opening of a pseudogap under this temperature. At the same time, a minimum value exists in the thermopower at certain temperature, which is the manifest of carrier localization. At about 50K, a clear peak of phonon-drag was observed in thermopower, and its positive value shows a change of sign in charge carrier at low temperature, which is in accordance with the change of slope in Hall coefficients.

 

Keywords: perovskite phase superconductors, transport properties, thermoelectric power

PACC:     7470V, 7430F, 7430J

 

 

³¬µ¼²ÄÁϵÄÕý³£Ì¬ÏÂÔÓÖÊпÒýÆðµÄ·Ç¾ùÔÈÐÔ

 

ËΠ óÞ

±±¾©Ê¦·¶´óѧÎïÀíϵ, ±±¾©  100875

 

±¾ÎIJÉÓú¬ÓзǴÅÐÔÔÓÖʵĶþάt-JÄ£ÐÍÀ´ÃèÊö²ôпµÄ¸ßÎÂÑõ»¯Îﳬµ¼²ÄÁÏ£¬²¢ÀûÓ÷ǾùÔÈ˫ʱ¸ñÁÖº¯ÊýÀíÂÛ¶ÔÓÐÏ޳ߴçµÄ²ÄÁϽøÐÐÁËÊýÖµ¼ÆËã.ÔÚ Fermion-Spin ÀíÂÛ¿ò¼ÜÏ£¬ÎÒÃÇ·Ö±ðÑо¿ÁË·Ç´ÅÐÔÔÓÖÊÒýÆðµÄµçºÉºÍ×ÔÐýµÄ²»¾ùÔÈÐÔ¼°¶Ô²ÄÁÏÕý³£Ì¬ÌØÐÔµÄÓ°Ïì.ÎÒÃÇ·¢ÏÖ£ºÒ»·½Ãæ·Ç´ÅÐÔÔÓÖÊп¶ÔÆ丽½üµÄ×ÔÐý·´Ìú´Å¹ØÁªÓÐÇ¿ÁÒµÄÓ°Ï죬ÄÜʹÖÜΧµÄ×î½üÁÚ¹ØÁªº¯ÊýµÄ¾ø¶ÔÖµ±È¾ùÔÈÇé¿öÔö¼ÓºÜ¶à£»ÁíÒ»·½Ã棬¿Õλ×Ó»áÊܵ½ÆäÖÜΧ×ÔÐýµÄÓ°Ïì¶ø³öÏÖÏàÓ¦µÄ·Ö²¼²»¾ùÔÈÐÔ£¬½ø¶øÓÖÓ°Ïì×ÔÐý¹ØÁªµÄ²»¾ùÔÈÐÔ.²¢ÇÒ£¬Î§ÈÆÔÓÖÊпÄܹ»ÐγÉ×ÔÐý¼¤·¢ºÍ¿Õλ¼¤·¢µÄ¾ÖÓò̬.

 

¹Ø¼ü´Ê£ºt-JÄ£ÐÍ£¬Fermion-SpinÀíÂÛ£¬ÔÓÖÊп

PACC:   7420M, 7430J, 7540M

 

 

 

INHOMOGENEITY INTRODUCED BY

Zn IMPURITY IN DOPED CUPRATES

 

SONG YUN

Department of Physics, Beijing Normal University, Beijing  100875

(Received 11 April, 2003)

 

Two-dimensional t-J model with nonmagnetic Zn impurities is studied based on the fermion-spin theory. Within an improved Green function theory, we perform numerical calculation for the  finite lattices with periodic boundary conditions, and obtain the inhomogeneities of hole concentration and local antiferromagnetic correlations around the nomagnetic Zn impurities. It is shown that the spin excitations are strongly influenced by the nonmagnetic impurities because the local antiferromagnetic correlations closest to the impurities are enhanced. The nearest-neighbor spin correlations also have strong effect to the energy of hole, as a result a bound state of hole is formed around the nonmagnetic Zn impurity.

 

Keywords£ºt-J model, fermion-spin theory, Zn impurity

PACC:     7420M, 7430J, 7540M

 

 

 

 

Cu-Ni°üÌ×MgB₂´øÓ¦Á¦Ð§Ó¦Ñо¿

 

¸µÃôÒã¹  Å˹úÎÀ¹  ½¹Õý¿í¹  ¶¡Á¢È˲

ÕÅ  Ó²  ³ÂÖÎÓѲ  º«ººÃñ²  ³Â¾´ÁÖ²

¹Õã½­´óѧÎïÀíϵ£¬º¼ÖÝ  310027

²Öйú¿ÆѧԺµÈÀë×ÓÌåÎïÀíËù£¬ºÏ·Ê  230031

 

ʹÓõç²âÁ¿·½·¨²âÁ¿ÁËÓ÷ÛÄ©Ì׹ܣ¨PIT£©¹¤ÒÕÖƱ¸µÄCu-Ni°üÌ×MgB₂µ¥Ð¾´øµÄµ¯ÐÔÄ£Á¿E,ÆäÖµÓëCu¼°ÆäºÏ½ðµÄµ¯ÐÔÄ£Á¿ÎªÍ¬Ò»Á¿¼¶£¬»¹Ö¤ÊµÁËÔÚ´øÖдæÔÚ×ÅѹËõÔ¤Ó¦Á¦.ÎÒÃÇÑо¿Á˸ôøÔÚ4.2K£¬0.5¡«4T´Å³¡ÏÂÍäÇú³É²»Í¬ÇúÂÊʱµÄI_c-BÌØÐÔÇúÏߣ¬²¢ÇÒ¼ÆËãÏàÓ¦ÇúÂÊʱµÄ×î´óÓ¦±äºÍÓ¦Á¦.ÍäÇúʵÑéÏÔʾ¸Ã´ø²Ä¶ÔÓ¦Á¦½ÏΪÃô¸Ð£¬±ØÐë¸Ä½ø¹¤ÒÕ²¢ÊµÊ©»úеǿ»¯.

 

¹Ø¼ü´Ê£º MgB₂´ø£¬ Ó¦Á¦Ð§Ó¦£¬ ʧ³¬¶¯Á¦Ñ§¹ý³Ì

PACC£º   7430L, 7470

 

RESEARCH ON STRAIN EFFECT ON

Cu-Ni SHEATHED MgB₂ SUPERCONDUCTING TAPE

 

                         FU MIN-YI¹  PAN GUO-WEI¹ JIAO ZHENG-KUAN¹  DING LI-REN²  ZHANG YONg²  CHEN ZHI-YOU² HAN HAN-MIN²  CHEN JING-LIN²

¹Physics Department of Zhejiang University, Hangzhou  310027

²Institute of Plasma Physics, Chinese Academy of Science, Hefei  230031

(Received 11 April, 2003)

 

The elastic modulus measurements of Cu-Ni sheathed MgB2 monofilament tape fabricated by ¡°power in tube¡± method have been performed using electric technique. The magnetic field dependence of I_c has been investigated on the sample subjected to various strain levels through bending of the tape with different radius. We found that our MgB₂ sample is sensitive to applied strains, mechanical reinforced MgB₂ tape is essential to practical application. The bend strain and stress have been calculated based on a formula derived from the definition.

 

Keywords: MgB₂ monofilament, Strain effect, Dynamics process of quench

PACC:     7430L, 7470

 

 

ɨÃèSQUIDÏÔ΢¾µµÄÑÐÖÆ

¼°ÆäÔڴųÉÏñºÍÎÞËð¼ì²âÖеÄÓ¦ÓÃ

 

ÕÅ·å»á¹  ¶¡ºìʤ^1,2  ºÎÔ¥Éú¹  ³ÂâÙ»ª¹  º«Ê¿¼ª¹

¶­ÊÀÓ­¹  ÑÕÏþÃ÷³   ÑîǬÉù¹  ³ÂÕ×¼×¹  ½ð  îì¹

¹Öйú¿ÆѧԺÎïÀíÑо¿Ëù£¬ ±±¾©  100080

²±±¾©¿Æ¼¼´óѧÎïÀíϵ£¬ ±±¾©  100083

³Öйú¿ÆѧԺÀí»¯¼¼ÊõÑо¿Ëù£¬ ±±¾©  100080

 

ÑÐÖÆÁËÁ½ÖÖÓÃÓÚ¼ì²âÊÒÎÂÑùÆ·µÄ³¬µ¼Á¿×Ó¸ÉÉæÆ÷£¨SQUID£©É¨Ãè´Å³¡ÏÔ΢¾µ£¨ÒÔϼò³ÆɨÃèSQUIDÏÔ΢¾µ£©£¬Ò»ÖÖʹÓó£¹æµÍT_c£¨Nb£©SQUIDÆ÷¼þ£¬ÁíÒ»ÖÖʹÓøßΣ¨YBCO£©SQUIDÆ÷¼þ.SQUID°²×°ÔÚÄÚ¶ÅÍߵײ¿µÄÀäÖ¸µ×¶Ë£¬Íâ¶ÅÍߵײ¿ÓÐ60¡«75΢Ã׺ñµÄ°×±¦Ê¯´°¿Ú£¬±»²âÑùÆ·´¦ÓÚÊÒÎÂ״̬λÓÚ´°¿ÚÏ£¬SQUIDÓë±»²âÑùÆ·Ö®¼äµÄ¼ä¾àͨ¹ý²¨ÎƹܵÄÉìËõ½øÐе÷½Ú.³£¹æµÍT_c£¨Nb£©Æ÷¼þϵͳµÄ¿Õ¼ä·Ö±æÂÊÓÅÓÚ140¦Ìm£¬´Å³¡ÁéÃô¶ÈÓÅÓÚ3pT/Hz^1/2£¬¸ßΣ¨YBCO£©Æ÷¼þϵͳµÄ¿Õ¼ä·Ö±æÂÊ¡«500¦Ìm£¬´Å³¡ÁéÃô¶È¡«46pT/Hz^1/2.Á½Õß¾ùÄܳ¤Ê±¼äÎȶ¨µØ¹¤×÷ÔÚÎÞÆÁ±Î»·¾³ÖÐ.ÀûÓÃÁ½Ì¨É¨ÃèSQUIDÏÔ΢¾µ£¬½øÐÐÁ˶àÖÖÓÐÓ¦ÓüÛÖµµÄ´Å³ÉÏñʵÑéºÍÎÞËð¼ì²âÑо¿.

 

¹Ø¼ü´Ê£º SQUID£¬ ÏÔ΢¾µ£¬ ´Å³ÉÏñ£¬ ÎÞËð¼ì²âª¤

PACC£º   0755£¬ 8170L

 

 

 

A SCANNING SQUID MICROSCOPE AND ITS APPLICATIONS FOR

MAGNETIC FIELD IMAGING AND NONDESTRUCTIVE EVALUATION

 

ZHANG FENG-HUI¹   DING HONG-SHENG^1,2   HE YU-SHENG¹   CHEN GENG-HUA¹

HAN SHI-JI¹   DONG SHI-YING¹   YAN XIAO-MING³   YANG QIAN-SHENG¹   CHENG ZHAO-JIA¹   JIN DUO¹

¹Institute of physics, Chinese Academy of Sciences, Beijing  100080

²Department of Physics, University of Science and Technology Beijing  100083

³Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing  100080

(Received 11 April, 2003)

 

We have built two scanning SQUID microscope for room temperature samples with LTS SQUID and HTS (YBCO) SQUID respectively. SQUIDs are mounted on the low end of the finger in Dewar. A thin sapphire window separates SQUIDs and samples. Samples stay in room temperature. The distance between SQUIDs and samples can be adjusted with a bellow. The LTS SQUID microscope has a field sensitivity superior to 3pT/Hz^1/2 and spatial resolution better than 140¦Ìm. The HTS SQUID system is of ¡«46pT/Hz^1/2 field sensitivity and ¡«500¦Ìm spatial resolution. Both microscopes can stably work for a long time in unshielded environment. We also have used them to do some interesting experiments for magnetic field

imaging and nondestructive evaluation (NDE).

 

Keywords: SQUID, microscope, magnetism imaging, nondestructive evaluation

PACC:     0755, 8170L

 

 

 

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