Unexpected High Spin Polarization in Cr4 Cluster

Recent X-ray magnetic circular dichroism (XMCD) spectroscopy has demonstrated a total high spin ground state of S = 11/2 in the Cr2+ cluster. The accuracy of these experiments opens the possibility to observe small magnetic particles with greater detail than those obtained in Stern–Gerlach setups. Particularly the chromium clusters, where a high total magnetization can be observed due to their localized d-electrons, are an excellent candidate to be detected in this sophisticated experiments. In this work, the small-sized chromium tetramer has been investigated in detail by means of zero and finite temperature ab initio methods. The dimer and trimer chromium clusters are reported as a benchmark in order to establish a reliable approach. We found the existence of a spin competition between a lower S = 1 and a higher S = 6 spin state in the Cr4 cluster; both spin states are close in geometry, allowing a spin-flip due to an spin–orbit coupling mechanism.