Residual polarization of negative muons implanted in C60 and K3C60

Negative muons captured by atoms with zero nuclear spin usually retain about 1/6 of their initial spin polarization P_0 after cascading down to their lowest Bohr orbital. This is particularly observed for μ^- implanted into graphite and diamond. However, μ^- implanted into a powder of the fullerene C₆₀ are found to show essentially zero residual polarization. A residual polarization of \sim P_0/6 is again seen in metallic K₃C₆₀. We speculate that these results are to be explained on the basis of hyperfine effects after completion of the muonic cascade. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electrical resistivity of some La-Sr-Nb oxides to 77 K

The electrical resistivity of compounds having compositions LaSr₂Nb _x ,O _y LaSrNb _x O _y , and La₂SrNb _x O _y , prepared by arc melting under argon atmosphere, is determined from 77 to 300 K. Low resistivity compositions are found in these systems for x > 2 and niobium in divalent state. None of the compounds investigated showed large resistance drop reported by Oguchi et al. (1987) in La-Sr-Cu-O compounds prepared by sputtering La₂CuO₄ on niobium substrate and attributed to possible superconductivity about 250 K.     

K3C60晶体中的电子屏蔽效应

用屏蔽的静电库仑相互作用势,引入各离子的屏蔽参数,并考虑离子间的短程相互作用,计算了K3C60晶体中各离子和原胞的结合能随屏蔽参数的变化.分析计算表明K3C60晶体中电子的屏蔽主要是指对钾离子势能的屏蔽,特别是对四面体空隙中的钾离子K+T,虽然屏蔽参数很小,但对晶体结构的稳定极为重要.     

Electrical resistivity of iron-vanadium alloys between 78 and 1200 K

Electrical resistivity (?) of FeV alloys containing 0.5, 0.9, 2.7, and 6.1 at% V has been measured as a function of temperature (T) between 78 and 1200 K. The ? vs. T curves exhibit a change in the slope at the ferromagnetic Currie temperature (T_c). The d?/dT vs. T curves in the neibhorhood of T_c are similar to the corresponding plot for pure Fe. Our studies confirm the previously observed anomalous effect of V on T_c of Fe, i.e., that T_c increase with small additions of V to Fe. The critical index λ⁺ associated with the power law of d?/dT just above T_c has been determined as a function of V concentration.