Magnetosynthesis Effect on the Structure and Ground State of Cu ²⁺ -Based Antiferromagnets

Synthetic variables can have an outsized influence on the crystal structure and magnetic properties of a material, particularly those of quantum materials. In this work, we investigate the impact of synthesis under a magnetic field (magnetosynthesis) on the crystal structure and magnetic properties of several Cu²⁺ (<i>S</i> = 1/2)-based materials with antiferromagnetic interactions and varying levels of magnetic frustration, from simple antiferromagnets to a quantum spin liquid. Here, we develop methods to apply small (0.09-0.37 T) magnetic fields during low-temperature hydrothermal, evaporative, and rehydration syntheses of the simple antiferromagnet CuCl₂·2H₂O, the canted antiferromagnet (Cu,Zn)₃Cl₄(OH)₂·2H₂O, the frustrated and canted antiferromagnet atacamite Cu₂(OH)₃Cl, and the highly frustrated quantum spin liquid herbertsmithite Cu₃Zn(OH)₆Cl₂. We report the first single-crystal X-ray structural determination of the Cu₃Cl₄(OH)₂·2H₂O structure type and probe the stability of this phase both experimentally and computationally. Atacamite Cu₂(OH)₃Cl synthesized under a 0.19 T field experiences a 0.15 K (∼3%) decrease in its Néel transition temperature. This result suggests that magnetosynthesis with small applied fields may have a very subtle influence upon the magnetic properties of moderately magnetically frustrated 3<i>d</i> materials.