Quasi One-Dimensional Spin System in Langmuir-Blodgett Films of a Charge-Transfer Complex

Abstract

The ESR spectra of conductive Langmuir-Blodgett (LB) films of N-docosylpyridinium-(TCNQ) ₂ are observed at the X and K bands. The spectrum simulation method is adopted to analyze these spectra, which show clear out-of-plane anisotropy, in order to obtain information concerning the magnetic and structural properties of the system. The analysis reveals that the linewidth anisotropy is dominated by the exchange-narrowed secular dipolar width peculiar to quasi one-dimensional spin systems. This result is consistent with the temperature dependent spin susceptibility data of the system, which has been found to be explained by the random-exchange Heisenberg antiferromagnetic chain model. These facts indicate the development of one-dimensional spin chains in the LB films. In addition, the orientation of TCNQ molecule is estimated from the spectrum analysis.