# Structural, magnetic, and spin dynamical properties of the polar antiferromagnets Ni$$_{3−x}$$Co$$_x$$TeO$$_6$$(x=1,2)

Skiadopoulou, Stella, Retuerto, Maria, Borodavka, Fedir, Kadlec, Christelle, Kadlec, Filip, Míšek, Martin, Prokleška, Jan, Deng, Zheng, Tan, Xiaoyan, Frank, Corey, and others. (2020) Structural, magnetic, and spin dynamical properties of the polar antiferromagnets Ni$$_{3−x}$$Co$$_x$$TeO$$_6$$(x=1,2). Physical Review B, 101 (1). Article Number 014429. ISSN 2469-9950. E-ISSN 2469-9969. (doi:10.1103/PhysRevB.101.014429) (KAR id:79663)

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## Abstract

We present results of a multimethod investigation of the polar antiferromagnets Ni$$_2$$ CoTeO$$_6$$ and NiCo$$_2$$ TeO$$_6$$, inspired by the colossal magnetoelectric effect present in Ni$$_3$$ TeO$$_6$$. Both compounds crystalize in the same polar space group R3 as Ni$$_3$$ TeO$$_6$$, preserving the crystal symmetry at least from room temperature down to 2 K. Ni$$_2$$ CoTeO$$_6$$ and NiCo$$_2$$ TeO$$_6$$ undergo antiferromagnetic phase transitions at T$$_N$$ = 55 and 52 K, and spin-flop transitions at an external magnetic field of approximately 8 and 4 T, respectively. Both compounds present an incommensurate antiferromagnetic helical structure with spins lying in the a b plane, in contrast to the collinear one along the c axis in Ni$$_3$$ TeO$$_6$$. Moreover, dielectric anomalies are observed at their antiferromagnetic phase transitions, suggesting a magnetoelectric behavior. Spin and lattice dynamics studies by a combination of infrared, Raman, and terahertz spectroscopies were performed. Below T$$_N$$, in both Ni$$_2$$ CoTeO$$_6$$ and NiCo$$_2$$ TeO$$_6$$, low-frequency spin excitations extremely sensitive to external magnetic field were observed. At least one of these magnons was simultaneously seen in Raman and THz spectra of both compounds, therefore we propose to assign them to electromagnons.

Item Type: Article 10.1103/PhysRevB.101.014429 Divisions > Division of Natural Sciences > School of Physical Sciences Emma McCabe 22 Jan 2020 09:42 UTC 16 Feb 2021 14:10 UTC https://kar.kent.ac.uk/id/eprint/79663 (The current URI for this page, for reference purposes) https://orcid.org/0000-0001-5868-4570