Magnetic ordering of antiferromagnetic trimer system 2b·3CuCl ₂·2H₂O

In this paper, we present the magnetic properties of 2b·3CuCl ₂·2H₂O (b = betaine, C₅H11NO ₂). 2b·3CuCl₂·2H₂O is the first model substance for a two-dimensional S = 1/2 orthogonal antiferromagnetic trimer system. We have performed magnetic susceptibility, magnetization curve, and specific heat under extreme conditions: low temperatures and high magnetic fields in this system. The experimental results indicate that this substance is a magnetically S = 1/2 antiferromagnetic trimer system. The magnetization also shows one-third of the saturation value (M_S ∼ 3.2μ_B/f.u.) between 5 and 14T The specific heat in a zero field shows a sharp peak at 1.38K corresponding to a long-range magnetic ordering, T_N. As the magnetic field increases, the T_N shifts remarkably to a lower temperature and is suppressed. Above 5T, the specific heat has no anomaly down to 150mK In the plateau region with an energy gap, the magnetic ordering seems to be disappeared.