Pd. Sacramento, THERMODYNAMICS OF A SPIN-S' IMPURITY IN A SPIN-S ANTIFERROMAGNETIC HEISENBERG CHAIN, Journal of physics. Condensed matter, 5(37), 1993, pp. 6999-7008
The numerical solution of the Bethe ansatz equations of an integrable
SU(2)-invariant generalization of the spin-S antiferromagnetic Heisenb
erg chain (Takhtajian-Babujian model) with a spin-S' impurity in zero
magnetic field is presented. The entropy, specific heat and susceptibi
lity of an impurity of spin S' are obtained numerically as a function
of the spin S of the chain. Three situations have to be distinguished:
(i) if S' = S the impurity just corresponds to one more site in the c
hain; (ii) if S' > S the impurity spin is only partially compensated (
undercompensated) at T = 0, leaving an effective spin of (S' - S); (ii
i) if S' < S (overcompensated) the entropy has an essential singularit
y at T = h = 0, giving rise to critical behaviour as h and T tend to z
ero. These properties are in close analogy with those of the n-channel
Kondo problem. The thermodynamics of the two models is compared.