Slow relaxation of magnetization in the Co(II)‐phosphotungstate Keggin polyoxometalate

Abstract

We are reporting the single crystal structure of the tetrabutylammonium (TBA) salt of the old Co(II) Keggin phosphotungstate anion (Co(II)POM) and a study of the magnetic behaviour of this well-known POM. This Co(II)POM crystallizes in a cubic cell and this high symmetry obscure a precise characterization of Co(II) coordination sphere metrics due to positional disordered. We employed DFT and SA-SOC-CASSCF as auxiliary tools to complement DC and AC magnetic data collected. The studied complex behaves as a fieldinduced single ion magnet (SIM) showing slow relaxing magnetization below 5 K under small DC applied magnetic fields. Raman relaxation mechanisms dominates with different relaxation times observed when switching from the TBA salt to the K salt of the Co(II)POM.