Molecular magnets are chemical objects consisting of magnetic metal ions and matching ligands which are synthesized in form of rings, chains, horseshoes, clusters or cages of spins. These magnetic structures are potential building blocks of future devices for information storage, quantum information processing and lead to a better understanding of magnetism at the atomic scale. In the talk we review our results of comprehensive study of the chromium-based molecular rings with bond defects and some 3d metal impurities as well as some homo and hetero-metallic clusters and chains with non-collinear anisotropy axes.

We focus on effects of anisotropy, geometry and frustration appearing in thermodynamic and dynamic properties of the nanoscale magnets which are described by Heisenberg-like spin models and can be simulated by accurate numerical methods. We reach the remarkable consistency of the DFT estimates of the magnetic couplings in pure and doped octanuclear chromium molecule and provide strong support to the spin models exploited in the literature.