层状钙钛矿钴氧化物Y1-xGdxBaCo2O5中稀土离子半径对电荷有序转变的影响

研究了层状钙钛矿钴氧化物Y1-xGdxBaCo2O5(x=0,0.25,0.5,0.75,1)的结构和输运性质,结果显示它们具有相似的相变行为,从而证明GdBaCo2O5与YBaCo2O5一样,也存在电荷有序转变.结果还表明电荷有序转变温度随稀土离子半径增加而上升.     

YBa2Cu3O7-δ外延薄膜的不可逆线与磁通玻璃线

在0—10T磁场范围内,系统地测量了YBa₂Cu₃O_7-δ外延薄膜处于磁场平行和垂直膜面两种情况下的R-T曲线和I-V曲线, 并对该样品的不可逆线和磁通玻璃线作了直接的比较.结果表明, 由不同约化电阻率判据给出的不可逆线和磁通玻璃线遵守相同的H∝(T(0)-T(H))ⁿ 关系.对于不可逆线, n=3/2,对于磁通玻璃线,n=4/3.不可逆线的位置不仅与判据有关而且与测量电流密度也有关,磁通玻璃线位于不可逆线的下方.探讨 关键词：     

He-O_2转动激发截面的理论计算

用公认精确的密耦 (Close Coupling)方法、采用两种不同的相互作用势计算了He -O2 碰撞的态 态转动激发截面 (E =2 6.8meV) ,通过系统研究和计算发现 :低能散射时 ,He -O2 碰撞的弹性散射主要发生在小角部分 ,而非弹性转动激发主要发生在大角部分。研究表明 :转动激发截面对势能表面的方向性和散射角都非常敏感。     

ANISOTROPY OF CRITICAL CURRENT DENSITY IN c-AXIS ORIENTED EPITAXIAL YBa2Cu3O7-δ FILMS

The dependence of critical current density J_c on the angle α between the directions of the applied magnetic field H (which was rotated in the c-axis-I plane) and the in-plane current I was measured on a c-axis oriented epitaxial YBa₂Cu₃O_7-δ films at 81 K, with the magnetic field strength up to 6T, Analysis of the experimental results on the basis of the classical scaling law of pinning force shows that there exist simultaneously planar-pinning and volume-pinning mechanisms, and the contribution of volume pinning increases wish decreasing while that of the planar pinning decreases, We propose that the decrease of Lorentz-force-independent critical current density with increasing H for H∥I results from the suppression of superconductivity by the magnetic field, The fact that the contribution of volume pinning increases with decreasing α also arises from the suppression of superconductivity in CuO₂ plane by the magnetic field.     

晶粒尺寸对Pr0.5(Ca0.47Ba0.03)MnO3中台阶效应的影响

采用溶胶-凝胶法制备了不同颗粒尺寸的Pr0.5(Ca0.47Ba0.03)MnO3多晶样品.对样品进行电阻测量发现,随颗粒边界的减小,其电阻率随磁场的变化即ρ(H)曲线上台阶数目和位置发生变化;实验同时发现,热循环对样品低温下的基态也有很大的影响.实验结果表明,颗粒尺寸大小,可以有效地调节反铁磁相(AFM)和铁磁相(FM)之间的相互作用,从而对台阶效应产生影响.进一步证明了台阶效应与相应力有关.     

Magneto-Orientated Graphite Double-Layer Homo-Structure with Broadband Microwave Absorption

We utilized magnetic fields as an efficient tool to manipulate the orientation and electromagnetic properties of graphite micro-flakes(GMFs). As a result, we successfully developed a GMF double-layer homo-structure,which shows excellent electromagnetic absorption properties. By tuning the direction of a small magnetic field(850 G), vertical and horizontal aligned GMFs are produced. Their electromagnetic parameters are effectively tailored by this magneto-orientation effect, and the vertical and ...