Low-temperature thermodynamic properties of a random Heisenberg antiferromagnetic chain (S=1/2)

The low-temperature thermodynamic properties of a random antiferromagnetic Heisenberg chain in zero magnetic field are studied approximately by a renormalisation group method. The couplings J obey a probability distribution function P(J) approximately 1/J alpha , with alpha a constant. It is found that the susceptibility chi and the specific heat C behave like chi approximately T - alpha chi and C approximately T 1- alpha c at low temperatures alpha chi and alpha c are weakly varying functions of temperature and slowly approach unity as T goes to zero. Comparison of these results with other theoretical analysis as well as experimental results on organic charge transfer compounds is also discussed.