High-field magnetic properties of the magnetic molecule {Cr 10Cu2}

We present detailed magnetic measurements and the theoretical analysis of the recently synthesized magnetic molecule { Cr10 Cu2 }. Due to the heterometallic nature of this molecule, there are three distinct intramolecular interactions, which we describe using an isotropic Heisenberg model with three distinct exchange constants. The magnetic properties of the model are calculated using the quantum Monte Carlo method, including the low-field magnetic susceptibility χ (T) and the magnetization M (H,T) versus magnetic field H up to the saturation field (≈80 T) for arbitrary temperature T. Of particular relevance to experiment, we have calculated the full set of ground-state level-crossing fields corresponding to peaks in ∂M/∂H versus H for low T. A detailed search of the three-dimensional parameter space yields two well-separated sets of exchange constants, both of which give good agreement between the predictions of the model and the measured χ (T). The present low-temperature tunnel-diode resonator measurements provide values of ground-state level-crossing fields, as well as the level-crossing fields for certain low-lying excited states up to 16 T that are in good agreement with theory. The full set of theoretical crossing fields is very nearly equal for both sets of exchange constants. The theory also provides quantitative predictions for the site-dependent local magnetic moments of this molecule, which could perhaps be tested by future nuclear-magnetic-resonance measurements. © 2009 The American Physical Society.