Effect of anisotropy on the temperature dependence of conductivity and magnetoconductance in heavily doped polyacetylene

Summary form only given. The temperature dependence of the conductivity and the magnetoresistance (MR) of heavily doped Shirakawa polyacetylene are measured for samples with different stretching ratio (1/1/sub 0/= 1/spl sim 6/). Unoriented samples show a strong temperature dependence of conductivity with the characteristic resistivity ratio Pr=P(I.4K)/p(300K)/spl sim/10/sup 2/. The conductivity anisotropy(/spl sigma////spl sigma//spl perp/ increases with stretching ratio upto /spl sigma/////spl sigma//spl perp//spl ap/110 for 1/1/sub 0/=6. For the samples of 1/1/sub 0//spl ges/3 P/sub r//spl sim/3 and nearly independent of 1/1/sub/0 and chain direction. Application of high pressure decreases P/sub r/, for both parallel and perpendicular direction without any variation in its anisotropy of conductivity. The magnetoconductance measured at low temperature (T<4.2K) is negative for unoriented samples and positive for stretched samples. The magnitude of magnetoconductance depends on the direction of magnetic field with respect to the chain direction.