Anhydrous copper tellurite disulfate Cu₃TeO₃(SO₄)₂ featuring the coexistence of spin singlets and a long-range antiferromagnetic order

Anhydrous copper tellurite sulfate, Cu3TeO3(SO4)(2), has been synthesized via vapor transport reactions in sealed silica glass ampoules. In measurements of magnetization M, magnetic susceptibility & chi;, 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 Cu2+ ions were found to form magnetically silent dimers. A peak in dielectric permittivity & epsilon;, which accompanies the Neel order, allows considering Cu3TeO3(SO4)(2) as a magnetoelectric multiferroic material of the second type. Density functional theory calculations provided estimations of leading exchange interaction parameters.