高JcBi-2223银包套带材的电阻转变展宽与磁通钉扎

系统地研究了高J_cBi-2223相银包套带材在0—1T磁场下的电阻转变展宽.实验结果表明,Bi-2223带材的电阻转变具有热激活的性质.研究了磁通钉扎势与温度的关系,得到电阻转变曲线的温度关系为R(T)=R₀exp{-u₀(1-T/T_c)ⁿ/kT},其中磁场平行于ab面时,n=4.5;磁场垂直于ab面时,n=3.在磁场平行于ab面时,耗散与Lorentz力无关,只与平行于ab面的磁场大小有关,这可 关键词：     

转动弹簧的质心

在弹簧质量不能忽略的情况下,采用最小势能原理,推导了弹簧做圆周运动时非均匀形变的数学表达式,讨论了此时弹簧的质量分布和质心位置问题。     

烧结Bi(Pb)SrCaCuO大块超导体的磁通蠕动

实验研究了 Bi(Pb)SrCaCuO 大块超导体在77.3K 下,50—2000Oe 磁场范围的磁通蠕动速率以及在150Oe、300Oe 磁场下磁通蠕动速率与温度的关系.并估算了它的磁通钉扎势,在77.3K 下,磁通钉扎势符合 U_o∝H~(-α)关系,且在50—800Oe 磁场范围α=0.87;在800—2000Oe 磁场范围α=0.28;在一定磁场下,液氮温度以上磁通钉扎势 U_o 随温度的升高而减小.     

低场下高度c轴取向的Bi2233银包套带材的反常霍尔效应研究

低场下高度ｃ轴取向的Ｂｉ２２３３银包套带材的反常霍尔效应研究姜柳笛，孙玉平，许国阳，杜家驹中国科学院固体物理研究所，合肥２３００３１中国科学技术大学结构分析开放实验室，合肥２３００２６１９９６年１０月３０日收到在低场（Ｈ＜１Ｔ）且磁场平行于ｃ轴（Ｈ／...     

碳纳米管/聚乙烯醇空心螺旋纤维的可控制备及其力学性能研究

提出一种通过控制钛丝直径和碳纳米管束可控制备碳纳米管/聚乙烯醇(CNTs/PVA)空心螺旋纤维的方法.该CNTs/PVA空心螺旋纤维在弯曲至原始长度1/3或拉伸至应变为100;时,电阻仍保持不变.CNTs/PVA空心螺旋纤维的最大拉伸应变高达600;.通过在氩气环境中500℃加热30 min退火处理后,CNTs/PVA空心螺旋纤维在30;的应变循环下,残余应变由原始的22;减小至2;,提高了CNTs/PVA空心螺旋纤维的力学性能.     

“数”山有路“趣”为径 “珠”海无边“乐”作舟

<正>在珠心算教学中,儿童长时间与数字打交道,极易产生厌学情绪,但当儿童对珠心算产生兴趣时就会觉得乐在其中,使之对训练乐此不疲。在珠心算教学中,教师要尽量创造生动活泼、轻松愉快的课堂环境和气氛,让儿童在玩中学、乐中学。这样不仅提高教     

二维超导材料

以石墨烯为代表的二维材料在二维半导体等领域具有重要的应用价值,因此得到了广泛的研究。二维超导体不仅丰富了二维材料的物理内容,而且具有潜在的应用价值,已成为备受关注的超导前沿领域之一。文章回顾了二维超导材料的研究历史,重点介绍了几种具有代表性的(准)二维超导材料及其存在的物理问题,并对二维超导材料的研究进行了展望。     

Anomalous low-temperature heat capacity in antiperovskite compounds

The low-temperature heat capacities are studied for antiperovskite compounds AX M_3(A = Al, Ga, Cu, Ag, Sn, X = C,N, M = Mn, Fe, Co). A large peak in(C- γ T)/T~3 versus T is observed for each of a total of 18 compounds investigated,indicating an existence of low-energy phonon mode unexpected by Debye T~3 law. Such a peak is insensitive to the external magnetic field up to 80 k Oe(1 Oe = 79.5775 A·m-1). For compounds with smaller lattice constant, the peak shifts towards higher temperatures with a reduction of peak height. This abnormal peak in(C- γ T)/T~3 versus T of antiperovskite compound may result from the strongly dispersive acoustic branch due to the heavier A atoms and the optical-like mode from the dynamic rotation of X M_6 octahedron. Such a low-energy phonon mode may not contribute negatively to the normal thermal expansion in AX M_3 compounds, while it is usually concomitant with negative thermal expansion in open-structure material(e.g., ZrW_2O_8, Sc F_3).     

Modulation of Insulator-Metal Transition Temperature by Visible Light in La7/8Sr1/8MnO3 Thin Film

Effects of magnetic field and light illumination on the electrical transport properties of La7/8Sr1/8MnO3 thin film grown on a Si substrate are investigated. The film shows an insulator-metal transition at Tp - 191.9 K and a low-temperature resistance minimum at Tmin ≈ 48 K in darkness. Both magnetic field and light illumination shift the insulator-metal transition temperature Tp to be higher, while the low-temperature transport properties of the film induced by them show different trends. That is, the magnetic field and light illumination make the Tmin shift to lower and higher temperatures, respectively. The enhancement of both Tp and Train under light illumination could be explained in terms of photoinduced hole-doping and demagnetization effects of La7 /8Sr1/8MnO3.     

(Bi,Pb)_2Sr_2CaCu_2O_y单晶的磁通钉扎研究

我们通过对重Pb掺杂的Bi-2212((Bi,Pb)-2212)单晶磁化性质的测量来研究磁通钉扎性能,发现样品中存在与温度有明显依赖关系的鱼尾效应,且此鱼尾效应不仅体现在磁滞洄线上,还体现在不同磁场下零场冷的M～T曲线的交叠上.同时我们采用非线性磁通蠕动模型,并考虑表面位垒和体钉扎的影响,运用数值模拟分析了样品的磁化性质,结果表明(Bi,Pb)-2212单晶的鱼尾效应源于重Pb掺杂导致样品各向异性的降低所引起的强的体钉扎效应,而高温的磁化性质主要取决于表面位垒的作用.