Measurement of interlayer spin diffusion in the organic conductor κ‐(BEDT‐TTF)2Cu[N(CN)2]Xκ‐(BEDT‐TTF)2Cu[N(CN)2]X, X=ClX=Cl, Br

In organic conductors the overlap integral between layers is small, in-plane momentum scattering is rapid and transport perpendicular to the layers is expected to be blocked. We present a high frequency conduction electron spin resonance (CESR) study in the layered organic metals κ‐(BEDT‐TTF)2Cu[N(CN)2]Xκ‐(BEDT‐TTF)2Cu[N(CN)2]X, X=ClX=Cl, Br, which verifies that the inter-layer spin hopping is effectively blocked. The method relies on resolving the CESR lines of adjacent layers in which the orientation of the g  -factor tensors differs. We find that at ambient pressure and in the metallic phase the electron spin diffusion is two dimensional in both the X=ClX=Cl and Br compounds, i.e. electrons diffuse longer than the spin lifetime within a single molecular layer without inter-layer hopping. Application of pressure at 250 K increases rapidly the inter-layer hopping rate of spins.