The mineral herbertsmithite, ZnCu3(OH)6Cl2, contains two-dimensional Kagome layers of Cu2+ (S=1/2) ions in O4Cl2 octahedra separated by layers of Zn2+ in O6 octahedra. It is a candidate for the long-sought-after spin-liquid ground state as no long range magnetic order is found above T = 50 mK despite strong antiferromagnetic interactions, ?CW ~ -300 K. However, the less interesting alternative, that Zn-Cu site mixing suppresses the magnetic phase transition, has not been excluded due to difficulties in quantifying the degree of Zn-Cu disorder. Here structural and magnetic properties on chemically related systems in which Zn2+ is replaced by Mg2+ and Cd2+ are presented. These results permit direct identification of the effect of disorder on the observed magnetic behavior, and highlight the importance of the Cu-O-Cu bond angle in determining the magnetic coupling between Cu2+ ions within each layer.

Effects of disorder and bond angle on the magnetic properties of ZnCu3(OH)6Cl2-like materials

239th National Meeting (2010)

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