Structural and spectroscopic properties of the polar antiferromagnet Ni2MnTeO6

Abstract

We present a structural and spectroscopic study of the compound Ni2MnTeO6, closely related to the polar antiferromagnet Ni3TeO6 known to show a colossal magnetoelectric effect and pronounced elementary magnetoelectric excitations. We prepared single crystals and polycrystalline samples of Ni2MnTeO6 showing the same polar structure as Ni3TeO6 from room temperature down to 4 K with the R3 space-group symmetry. Magnetic and dielectric measurements have indicated an antiferromagnetic phase transition at T-N approximate to 70 K, almost 20 K higher than that of Ni3TeO6. Extensive infrared, Raman, and terahertz spectroscopy experiments were employed for investigating lattice and spin excitations, revealing all phonons predicted by the factor group analysis. Terahertz spectra below TN reveal one new excitation, which is strongly influenced by external magnetic field, thus assigned to a magnon.