We study the ground-state properties of frustrated Heisenberg ferrimagneticladders with antiferromagnetic exchange interactions and two types ofalternating sublattice spins. In the limit of strong rung couplings, we showthat the mixed spin-1/2 and spin-1 ladders can be systematically mapped onto aspin-1/2 Heisenberg model with additional next-nearest-neighbor exchanges. Thesystem is either in a ferrimagnetic state or in a critical spin-liquid statedepending on the competition between the spin exchanges along the legs and thediagonal exchanges.
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