  The purpose of the present paper is two-fold. On the one hand, we review some
recent studies on the low-temperature strong-field thermodynamic properties of
frustrated quantum spin antiferromagnets which admit the so-called
localized-magnon eigenstates. One the other hand, we provide some complementary
new results. We focus on the linear independence of the localized-magnon
states, the estimation of their degeneracy with the help of auxiliary classical
lattice-gas models and the analysis of the contribution of these states to
thermodynamics.
