ORDERING OF LOCALIZED MOMENTS IN KONDO-LATTICE MODELS

We describe the transition from a ferromagnetic phase, to a disordered paramagnetic phase, which occurs in one-dimensional Kondo lattice mod els with partial conduction band filling. The transition is the quantu m order-disorder transition of the transverse-field Ising chain, and r eflects double-exchange ordered regions of localized spins bring gradu ally destroyed as the coupling to the conduction electrons is reduced. For incommensurate conduction-band filling, the low-energy properties of the localized spins near the transition are dominated by anomalous ordered (disordered) regions of localized spins which survive into th e paramagnetic (ferromagnetic) phase. Many interesting properties foll ow, including a diverging susceptibility for a finite range of couplin gs into the paramagnetic phase. Our critical line equation, together w ith numerically determined transition points, are used to determine th e effective range of the double-exchange interaction. Models considere d are the spin-1/2 Kondo lattices with ferromagnetic and antiferromagn etic couplings, and the Kondo lattice with repulsive interactions betw een the conduction electrons. [S0163-1829(98)04326-4].