Static and dynamic magnetic properties of the spin-1/2 inequilateral diamond-chain compounds A_3Cu_3AlO_2(SO_4)_4 (A = K, Rb, Cs)

摘要

Spin-1/2 compounds A_3Cu_3AlO_2(SO_4)_4 (A = K, Rb, and Cs) have one-dimensional (1D) inequilateral diamond chains. We analyze the temperature dependence of the magnetic susceptibility and determine the magnetic exchange interactions. In contrast to azurite, a dimer is formed on one of the sides of the diamond. From numerical analyses of the proposed model, we find that the dimer together with a nearly isolated 1D Heisenberg chain characterize magnetic properties including magnetization curve and magnetic excitations. This implies that a dimer-monomer composite chain without frustration is a good starting point for describing these compounds.