Anhydrous copper tellurite disulfate Cu 3 TeO 3 (SO 4 ) 2 featuring the coexistence of spin singlets and a long-range antiferromagnetic order.

Anhydrous copper tellurite sulfate, Cu 3 TeO 3 (SO 4 ) 2 , has been synthesized via vapor transport reactions in sealed silica glass ampoules. In measurements of magnetization M , magnetic susceptibility χ , specific heat C p and X-band electron spin resonance, a long-range antiferromagnetic order at T N = 13 K and an H - T magnetic phase diagram have been established. One-third of Cu 2+ ions were found to form magnetically silent dimers. A peak in dielectric permittivity ε , which accompanies the Néel order, allows considering Cu 3 TeO 3 (SO 4 ) 2 as a magnetoelectric multiferroic material of the second type. Density functional theory calculations provided estimations of leading exchange interaction parameters.