Magnetism in the novel spin system Ni5(TeO3)4Br2 with two-dimensional frustrated geometry

A study of magnetism in the novel 2D spin system Ni5(TeO3)4Br2, featuring a frustrated triangular geometry, is presented. We combine magnetization, heat capacity and high-field electron spin resonance measurements to investigate a long-range magnetic ordering below TN = 29 K. Additional peculiar behaviour, most likely related to the spin system, is observed below T′ = 14 K.