Restricted diffusion, relaxation and absolute magnetic susceptibility of the conduction electrons in quasi one-dimensional organic conductors

Abstract

Abstract Pulsed electron spin resonance (ESR) is conveniently used for the analysis of spin dynamics in organic conductors - e.g. the derivation of spin-spin ( T 2 ) and spin-lattice ( T 1 ) relaxation times. If, in addition to the homogeneous magnetic field, a field gradient is applied, the diffusion constant ( D ) of the conduction electrons can be determined from the analysis of the echo decay. We show that restricted diffusion can be identified by analysis of the echo decay with help of Neuman's equations. An average diffusion length of 95.8μ m has been obtained for a Fluoranthene radical cation salt. For appropiate choice of the tipping angles, multiple spin echos can be observed after two excitation pulses, caused by the nonlinearity of the Bloch equations. We show for Fluoranthene and Perylene radical cation salts that their quantitative analysis allows the derivation of the conduction electrons' absolute magnetic susceptibility without sensitivity calibration of the spectrometer.