Structure and magnetism of S = 1/2 kagome antiferromagnets NiCu3(OH)6Cl2 and CoCu3(OH)6Cl2

Published 18 Dec 2011 in cond-mat.str-el, cond-mat.mtrl-sci, and cond-mat.supr-con | (1112.4117v3)

Abstract: We have successfully synthesized S = 1/2 kagome antiferromagnets MCu3(OH)6Cl2 (M = Ni and Co) by hydrothermal method with rotating pressure vessel. Structural characterization shows that both compounds have the similar crystal structure as ZnCu3(OH)6Cl2 with R-3m symmetry. Similar to ZnCu3(OH)6Cl2, the compounds show no obvious hysteresis at 2 K. A spin glass transition is found in both NiCu3(OH)6Cl2 and CoCu3(OH)6Cl2 at low temperatures (6.0 and 3.5 K respectively) by AC susceptibility measurements. It indicates no long-range magnetic order and a strong spin frustration. The substitution of Zn2+ by magnetic ions Ni2+ or Co2+, effectively enhances interlayer exchange coupling and changes the ground state of the kagome spin system.