REDUCED S-D MODEL WITH ANTIFERROMAGNETICALLY COUPLED IMPURITY SPINS

摘要

An antiferromagnetic equivalent-neighbour Heisenberg interaction H-i between impurity spins is added to the reduced s-d Hamiltonian H-r previously introduced by simplifying the Kondo s-d exchange Hamiltonian H-K. Asymptotic mean-field theory is developed for H-r + H-i, in the presence and absence of external magnetic field, and applied to (La1-xCex)Al-2 alloys. Specific heat C-i(T) and zero-field susceptibility chi(i)(0,T) curves for (La1-xCex)Al-2 are depicted. The coupling constants of H-r + H-i and conduction bandwidth are adjusted so that T, temperatures for x = 0.2, 0.1 are equal to the experimental values. C-i(T) exhibits a jump at T-c and is decreasing for T < T-c. chi(i)(0,T) has a first order pole at T-c which corresponds to the maximum of experimental susceptibility and chi(i)(0,0) > 0. These results improve those obtained earlier on the grounds of H-r theory. [References: 23]