Thermodynamics of spin 1/2 reduced s-d model with application to (LaCe)Al2 alloys

The Hamiltonian HK(B) of the spin 1/2 s-d exchange model in a uniform magnetic field B is reduced by a method previously applied to HK(0). The reduced s-d Hamiltonian Hr(B) is asymptotically equivalent in the thermodynamic limit to a mean-field hr(B), which exhibits a 2nd order phase transition at Tc if B is weak. hr(B) is applied to (LaCe)Al2 alloys. There is correspondence between theoretical and experimental curves of zero-field susceptibility χi(0, T): the theoretical χi(0, T) has a first-order pole at Tc, below the Kondo temperature TK; the experimental χie(0, T) curve has a finite maximum below TK. The zero-field theoretical specific heat of (LaCe)Al2 exhibits a finite discontinuity at Tc. Above Tc the expression for resistivity coincides with the one given by Kondo and the limiting T → 0 resistivity is finite