Magnetic properties of a doped quasi-triangular lattice material, Cu$_{2(1-x)}$Zn$_{2x}$(OH)$_{3}$NO$_{3}$/(C$_{7}$H$_{15}$COO)

Cu$_{2}$(OH)$_{3}$NO$_{3}$,is a geometrically frustrated layered compound in which spin S=1/2 Cu$^{2+}$ ions are arranged on a slightly distorted triangular lattice. The magnetic properties of the pure compound and of the compound intercalated with alkanecarboxylate have been extensively studied.[1] However, the effects of intralayer doping remain unexplored. The substitution of non-magnetic ions such as Zn$^{2+}$ for Cu$^{2+}$ will ultimately drive the ordering temperature toward zero [2] which may provide a candidate system possessing an exotic spin-liquid ground state. We have prepared powder samples of the Cu$_{2(1-x)}$Zn$_{2x}$(OH)$_{3}$NO$_{3}$ family and systematically investigated them by magnetic susceptibility measurements. The ordering temperature decreases from 11K to 5.6K while the C-W temperature increases from -5.1K to +2.8K as the Zn concentration increases from 0 to 65\%. To enhance the 2-dimensional characteristic and reduce the interlayer interaction, we introduce an alkanecarboxylate C$_{7}$H$_{15}$COO into the interlayer space. The experimental results we have obtained indicate that this new class of materials have much higher frustration levels $|\Theta_{cw}$ /T$_{c}|\sim$ 20 and order at a lower temperature than the doped parent compounds.\newline[1] M. A. Girtu et al, Phys Rev B 61,4117(2000).\newline[2] M. Mekata et al, J. Phys. Soc. Japan 56, 4544(1987).