Site-selective quantum correlations revealed by magnetic anisotropy in   the tetramer system SeCuO3
  We present the investigation of a monoclinic compound SeCuO3 using x-ray powder diffraction, magnetization, torque and electron-spin-resonance (ESR). Structurally based analysis suggests that SeCuO3 can be considered as a 3D network of tetramers. The values of intra-tetramer exchange interactions are extracted from the temperature dependence of the susceptibility and amount to ~200 K. The inter-tetramer 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. 
I. \v{Z}ivkovi\'c, D. M. Djoki\'c, M. Herak, D. Paji\'c, K. Pr\v{s}a,   P. Pattison, D. Dominko, Z. Mickovi\'c, D. Cin\v{c}i...
cond-mat.str-el cond-mat.mtrl-sci