High-field magnetic properties of the magnetic molecule {Cr10Cu2}

We present detailed magnetic measurements and the theoretical analysis of the recently synthesized magnetic molecule {Cr10Cu2}. 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 chi(T) and the magnetization M(H,T) versus magnetic field H up to the saturation field (approximate to 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 partial derivative M/partial derivative 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 chi(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.