Frustrated magnetism in doped quasi-triangular lattice materials, Cu$_{2(1-x)}$Zn$_{2x}$(OH)$_{3}$NO$_{3}$/(C$_{7}$H$_{15}$COO)

We have performed DC and AC magnetic susceptibility measurements on the spin S=1/2 quasi-triangular lattice materials Cu$_{2(1-x)}$Zn$_{2x}$(OH)$_{3}$NO$_{3}$/(C$_{7}$H$_{15}$COO). The X-ray diffraction experiments reveal that this class of materials has a crystal structure in P2$_{1}$/m space group, in which Cu$^{2+}$ and Zn$^{2+}$ ions are arranged on a slightly distorted triangular lattice [1]. Cu$_{2(1-)}$Zn$_{2x}$(OH)$_{3}$NO$_{3}$ with a short inorganic intercalation NO$_{3}$ group, have a long-range antiferromagnetic order at low temperature. The Neel temperature T$_{N}$ decreases from 11K to 5.6K while the Curie-Weiss temperature increases from -5.1K to +2.8K as the Zn concentration increases from 0 to 65\%. After a longer alkanecarboxylate C$_{7}$H$_{15}$COO group was introduced into the interlayer space, a spin-glass like behavior in magnetic properties was observed [2]. The value $|\Theta_{cw}$ /T$_{N}|$ is approximately 20, indicating the materials are in a medium level frustrated state. The onset of a ferromagnetic correlation was found in both DC and AC susceptibility data. The interplay of geometrical frustration and the coexistence of ferromagnetic and antiferromagnetic couplings has driven the materials into a glassy ground state. \newline [1] G. Linder, et al., Journal of Solid State Chemistry (1995) \newline [2] M. A. Girtu et al, Phys Rev B 61,4117(2000).