Effect of diamagnetic doping on the magnetic resonance in a quasi-one-dimensional system tetramethylammonium manganese trichloride.

Abstract

We present electron-spin-resonance data obtained on finite magnetic chains of ${\mathrm{CH}}_{3}$${\mathrm{NMn}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Cd}}_{\mathrm{x}}$${\mathrm{Cl}}_{3}$ (TMMC-Cd) for x=0.02, 0.09, and 0.2. The measurements were developed with the microwave field either parallel or perpendicular to the magnetic field. The longitudinal relaxation time was also measured in the x=0.02 and 0.09 samples. All our experimental results show a noticeable influence of the impurities on both the line shape and linewidth, contrary to previously published data. New nuclear magnetic resonance data dealing with high-frequency proton relaxation rates are also presented. A full treatment using the memory-function formalism has been carried out to account for the significant difference observed between pure and doped samples. Our experimental data are satisfactorily described by this theory and the model of correlation functions for finite chains.