The angle dependences of the magnetoresistance of two different isotopic substitutions (deuterated and undeuterated) of the layered organic superconductor $\kappa -\left(\mathrm{ET}{)}_2\mathrm{Cu}\right(\mathrm{NCS}{)}_2$ are presented (where ET is the organic molecule bis(ethylenedithio)-tetrathiafulvalene). The angle-dependent magnetoresistance oscillations (AMRO) arising from the quasi-one-dimensional and quasi-two-dimensional Fermi surfaces in this material are easily confused. By using the Boltzmann transport equation extensive simulations of the AMRO are made that reveal the subtle differences between the different species of oscillation. No significant differences are observed in the electronic parameters derived from quantum oscillations and AMRO for the two isotopic substitutions. The interlayer transfer integrals are determined for both isotopic substitutions and a slight difference is observed which may account for the negative isotope effect previously reported. The success of the semiclassical simulations suggests that non-Fermi liquid effects are not required to explain the interlayer transport in this system.

• Received 3 December 2003

DOI:https://doi.org/10.1103/PhysRevB.69.174509