AN ACCURATE MAPPING OF QUANTUM HEISENBERG MAGNETIC MODELS OF SPIN-S TO STRONG-COUPLING MAGNON SYSTEMS

An infinite-U term is introduced into the Holstein-Primakoff-transform ed magnon Hamiltonian of quantum Heisenberg magnetic models of spin s. This term removes the unphysical spin-wave states at every site, and automatically truncates the expansion in powers of the magnon occupati on operator. The resultant strong-coupling magnon Hamiltonians are acc urately equivalent to the original spin Hamiltonians. The on-site U-le vels and their implications are studied. Within a simple decoupling ap proximation for our strong-coupling magnon models, we can easily repro duce the results for the (sublattice) magnetizations obtained previous ly for the original spin model. But our bosonic Hamiltonians without a ny unphysical states allow substantially improved values to be obtaine d for the spectral weight in the ground state, and for ground-state en ergies lower than those obtained within previous approximations.