Kagome quantum spin systems in the atacamite family

Abstract

We present the hydrothermal synthesis, as well as structural and chemical analysis of single crystals on the compounds EuCu$_{3}$(OH)$_{6}$Cl$_{3}$, Zn$_{x}$Cu$_{4-x}$(OH)$_{6}$(NO$_{3}$)$_{2}$ and haydeeite, MgCu$_{3}$(OH)$_{6}$Cl$_{2}$ all arising from the atacamite family. Magnetic and specific-heat measurements down to 1.8 K are carried out for these systems. EuCu$_{3}$(OH)$_{6}$Cl$_{3}$ has a frustrated antiferromagnetic Cu$^{2+}$ ground state with order at 15 K, a strong anisotropy and increased magnetization from Van Vleck paramagnetic Eu$^{3+}$ contributions. ZnCu$_{3}$(OH)$_{6}$(NO$_{3}$)$_{2}$ reveals antiferromagnetic order at 9 K and measurements on haydeeite single crystals confirm the ferromagnetic order at 4.2 K with the easy axis within the kagome plane. These results prove that the atacamite family presents a broad class of materials with interesting magnetic ground states.