| The temperature dependence of the magnetic penetration depth ( lambda) has been measured in single crystals of fully deuterated kappa-(ET)2Cu[N(CN)2]Br. This material separates into superconducting (SC) and antiferromagnetic (AFI) phases. The relative amounts of SC and AFI phases has been shown to depend on the cooling rate of these materials in the vicinity of 80 K. In varying the cooling rate from 0.0025-180 K/min, the Meissner fraction appears to vary logarithmically with the cooling time, suggesting that these organics act like a glassy system near 80 K where SC nucleation grains are formed. In addition, the penetration depth of deuterated kappa-(ET)2Cu[N(CN) 2]Br consistently displays a power law temperature dependence with an exponent of n = 1.6-1.8 for Meissner fractions ranging from 0.03-0.60. This suggests that these samples are robust dirty d-wave superconductors like their undeuterated counterpart.;With abnormally large penetration depths resulting from traditional analysis, an aluminum plating technique was used to measure the absolute penetration depth of deuterated kappa-(ET)2Cu[N(CN) 2]Br. The large values of lambda(0) were confirmed with this technique. Measurements yielded values that increased from 29- 320 mum with increasing cooling rate. This finding motivated the development of a SC spherical grain model where the deuterated sample was assumed to be a collection of independent spheres of undeuterated kappa-(ET) 2Cu[N(CN)2]Br. The model yielded grain sizes on the order of 5-40 mum, which agrees well with literature. Also, high and low temperature data was checked for self consistency.;In addition to this work, the temperature dependence of the interplane penetration depth of undeuterated kappa-(ET)2Cu[N(CN) 2]Br was performed. With higher order corrections to the traditional analysis accounted for, a value of lambda⊥ = 130 mum was measured. Also, the temperature dependence of the superfluid density was similar to in-plane behavior, suggesting that interplane transport in these materials is coherent despite being highly anisotropic and definitely 2D in nature. |
