Measurements of the intermediate field magnetization of a random exchange heisenberg antiferromagnetic chain, quinolinium(TCNQ) 2

Measurements of the relative magnetization (M) and linewidth (ΔH {1}/{2}) of quinolinium(TCNQ) ₂ are reported using ESR at 9.5 GHz over the temperature range 0.054-4.2 K. The experiment was performed in a dilution refrigerator using an unconventional microwave technique. Throughout the entire temperature range, M fits the behavior expected of a random exchange Heisenberg antiferromagnetic chain on the basis of the ECP or Bulaevskii models using an exponent α = 0.81 ± .03. The linewidth has a slow, logarithmic divergence with decreasing temperature similar to that reported earlier for low frequency measurements.