Multianvil high-pressure/high-temperature synthesis and characterization of magnetoelectric HP-Co3TeO6

Abstract

By high-pressure/high-temperature multianvil synthesis a new high-pressure (HP) phase of Co₃TeO₆ was obtained. The compound crystallizes in the acentric trigonal crystal system of the Ni₃TeO₆-type structure with space group R3 and the following unit cell parameters and refinement results: a = 519.37(6) pm, c = 1382.4(2) pm, V = 322.93 ų, R₁ = 0.0150, wR₂ = 0.0374, GooF = 1.114 and a Flack parameter of 0.04(5). High-temperature powder X-ray diffraction (PXRD) measurements showed an exceptionally high-temperature stability of the HP-modification up to 1070 K. Magnetic measurements revealed an antiferromagnetic ordering below T_N = 58.2(1) K and a spin-flop-type transition at T = 3 K with a critical magnetic field of H_crit = 10.8(1) kOe. Magnetic and magnetoelectric (ME) transition temperatures were determined by specific heat measurements and exhibited a non-hysteretic behavior of the magnetoelectric coupling. Additionally, from the UV-Vis reflectance spectra a direct and an indirect band gap of E_g = 1.88 eV and E_g = 1.91 eV were calculated, underlining the semiconducting nature of HP-Co₃TeO₆.