Crystal water induced alteration of magnetic exchange interactions

Cuprates show an intimate interplay between the crystal structure and their magnetism, particularly with respect to frustration and dimensionality. On the other hand, it is a widespread belief that crystal water has just a moderate and quantitative influence to the magnetic properties of these compounds caused by the modification of interatomic distances. In contrast, the hydration of CuCl2 leads to a dramatic change in magnetic behaviour and ground state. While CuCl2·2H2O is a classic example for a three-dimensional antiferromagnet (TN 4.3 K) [1] with small exchange couplings, CuCl2 is a quasi-one dimensional chain compound that exhibits long-range order at T 24 K [2].