Site-selective quantum correlations revealed by magnetic anisotropy in the tetramer system SeCuO³.

We present the investigation of a monoclinic compound SeCu0³ using x-ray powder diffraction, magnetization, torque, and electron-spin-resonance. Structurally based analysis suggests that SeCu0³can be considered as a three-dimensional network of tetramers. The values of intratetramer exchange interactions are extracted from the temperature dependence of the susceptibility and amount to ~200 K. The intertetramer coupling leads to the development of long-range antiferromagnetic order at TN= 8 K. An unusual temperature dependence of the effective g tensors is observed, accompanied with a rotation of macroscopic magnetic axes. We explain this unique observation as due to site-selective quantum correlations. [ABSTRACT FROM AUTHOR]