Magnetic susceptibility of β′-[Pd(dmit)2] salts (dmit=1,3-dithiol-2-thione-4, 5-dithiolate, C3S5):: evidence for frustration in spin-1/2 Heisenberg antiferromagnets on a triangular lattice

The magnetic susceptibilities of a series of compounds, beta'-X[Pd(dmit)(2)](2) (X = Me4As, Me4P, Me4Sb, Et2Me2P, and Et2Me2Sb, where Me = CH3 and Et = C2H5), have been investigated. The temperature dependence of chi has been analysed in terms of the two-dimensional spin-1/2 Heisenberg antiferromagnet on the triangular lattice; it is the first time that this approach has been applied to experimental data. The observed X can be understood as reflecting the behaviour of the geometrically frustrated spins. The variation among the compounds suggests a role of frustration in relation to the relative stability of the metallic state.