ScholarWorks@성균관대학교

초록

We systematically investigate the structural, magnetic, and dielectric properties of polycrystalline samples Ni3-xCoxTeO6 (0 ≤ x ≤ 2.85). Powder X-ray diffraction reveals a structural transition from rhombohedral (R3) to monoclinic (C2/c) with increasing Co2+ substitution. The rhombohedral phase (R3) persists up to x ≤ 1.5, while x ∼ 2.55 and 2.85 adopt the monoclinic (C2/c) structure of Co3TeO6. Lattice parameters a and c increase linearly with Co2+ content, obeying Vegard's law. The DC magnetic susceptibility, χ(T), study reveals long-range antiferromagnetic ordering at TN ∼ 53 K and weak ferro/ferrimagnetic ordering at Tc ∼ 82 K for lower Co2+ substitution. As Co2+ content increases, TN shifts to ∼49 K, and Tc disappears at the critical concentration. For x ∼ 2.55, χ(T) reveals multiple magnetic transitions: short-range order at Tm ∼ 50 K, a cusp at TN1 ∼ 32 K, TN2 ∼ 28.3 K, and an abrupt change at 21.8 K. For higher substitution (x ∼ 2.85), these transitions shift slightly to lower temperatures, Tm ∼ 49.3 and TN2 ∼ 26.2, resembling Co3TeO6 except for the presence of Tm. All the measured samples show dielectric peaks near magnetic transitions, suggesting a magneto-dielectric effect. Our results demonstrate that Co substitution in Ni3TeO6 tunes both magnetic and dielectric properties across the composition range. Notably, compositions such as NCTO3 (x = 0.45) exhibit pronounced dielectric anomalies coinciding with magnetic transitions, indicating a coupling between spin and dielectric responses. This behavior points to composition-sensitive magnetoelectric interactions, underscoring the potential for tuning multiferroic functionalities within the Ni3−xCoxTeO6 solid solution. © 2025 Elsevier B.V.