Single crystal susceptibility measurements on CuCl2⋅2DMSO, A 1‐D S=1/2 quasi‐Heisenberg antiferromagnet

We report the results of magnetic susceptibility investigations of single crystals of CuCl2⋅2DMSO and of a polycrystalline sample of CuBr2⋅2DMSO, [DMSO=(CH3)2SO] two isostructural, orthorhombic linear chain S=1/2 compounds. The principal susceptibilities of the chloride all show rounded maxima near 11 K, then gradually decrease at different rates at lower temperatures. There is no indication of long range ordering above 2 K. All three susceptibilities show evidence of uniaxial anisotropy contributions within the exchange Hamiltonian with the b axis corresponding to the magnetic easy axis. The data are interpreted in terms of the results of Bucher and Honerkamp with an antiferromagnetic exchange constant of −8.2 K and 10% Ising‐like anisotropy. The susceptibility of the bromide can be described as a Heisenberg antiferromagnetic chain with J/k=−11.0(2) K above 40 K but at lower temperatures the susceptibility rises as if 7% of the moments were paramagnetic. Since this behavior is observed in different batch...