Transformation of in-plane ρ(T)\rho (T) in YBa2Cu3O7−δYBa_{2}Cu_{3}O_{7-\delta} at fixed oxygen content

This paper reveals the origin of variation in the magnitude and temperature dependence of the normal state resistivity frequently observed in different YBCO single crystal or thin film samples with the same $T_{c}$. We investigated temperature dependence of resistivity in $YBa_{2}Cu_{3}O_{7-\delta}$ thin films with 7- $\delta = 6.95$ and 6.90, which were subjected to annealing in argon at 400-420 K ($120-140^{o}C$). Before annealing these films exhibited a non-linear $\rho_{ab}(T)$, with a flattening below 230 K, similar to $\rho_{b}(T)$ and $\rho_{ab}(T)$ observed in untwinned and twinned YBCO crystals, respectively. For all films the annealing causes an increase of resistivity and a transformation of $\rho_{ab}(T)$ from a non-linear dependence towards a more linear one (less flattening). In films with 7- $\delta = 6.90$ the increase of resistivity is also associated with an increase in $T_{c}$. We proposed the model that provides an explanation of these phenomena in terms of thermally activated redistribution of residual O(5) oxygens in the chain-layer of YBCO. Good agreement between the experimental data for $\rho_{ab}(t,T)$, where t is the annealing time, and numerical calculations was obtained.Comment: 8 pages, 9 figures, submitted to PR

Forskellige systemers forventede produktionsmæssige, økonomiske og miljømæssige resultater

Selv om der de sidste fire år har været en kraftig stigning i den økologiske svineproduktion i Danmark, udgør den økologiske slagtesvineproduktion mindre end 0,5% af den totale slagtesvineproduktion, og erfaringsgrundlaget for gennemførelsen af den økologiske svineproduktion er derfor spinkelt. I mange tilfælde er svineproduktionen indrettet således, at søerne holdes på friland, mens slagtesvinene året rundt opstaldes i stalde med tilhørende udearealer, og det er for sådanne systemer, at videngrundlaget er bedst