Superconductivity and magnetic ordering in YBa₂(Cu_1-xFe_x)₃O₇

Transverse-and zero-field μSR measurements have been made for YBa₂(Cu_1-xFe_x)₃O₇ with x=0.04, 0.08 and 0.12. The temperature range studied was from approximately 7.5 K to 100 K. The onset of magnetic ordering commences at about 7.5 K for x=0.04, 10 K for x=0.08 and 20 K for x=0.12. The Gaussian depolarization parameter, σ of G_x(t) = exp(-σ²t²/2), is depressed by a factor of about 0.6 for x=0.04, but for the x=0.08 sample σ is depressed by a factor of 10 and increasing suppression is seen as the temperature is lowered below 45 K. This decrease in σ is interpreted in terms of decreasing electronic mean free paths.