Synthesis, Structure and Magnetic Properties of New Spin-Dimer Compound K2Cu2(Te2O5)(TeO3)2·2H2O

We have successfully synthesized a new transition metal tellurate compound K2Cu2(Te2O5)(TeO3)(2)center dot 2H(2)O. The compound crystallizes in the monoclinic crystal system with space group P2(1)/c; the Te coordination polyhedra polymerizes to form [Te2O5](8) ladders running along [100]. The ladders are connected in the [001] direction to the [Cu2O8] spin-dimer units via common oxygen to form covalently bonded [Cu2Te2O5](8). Magnetization measurements confirmed that K2Cu2(Te2O5)(TeO3)(2)center dot 2H(2)O has spin-dimer properties. The broad maximum around T-max = 50 K indicates the low-dimensional magnetic interaction and may be related to the existence of more than one spin dimer in the system. The perfect fitting of Bleaney-Bowers on magnetization curves shows the coexistence of two kinds of Cu-Cu dimers in K2Cu2(Te2O5)(TeO3)(2)center dot 2H(2)O, in which the two dimers show different intradimer and interdimer magnetic interactions resulting from the different Cu-Cu distances and different coordination circumstances. The experimental results indicate the magnetic properties of the dimer can be modulated using the crystalline coordination of the spin dimer.