Unravelling cation distribution and its role in tuning the magnetic and dielectric properties of V-modified cuprospinel

Abstract In this work, CuFe 2− x V x O 4 (0 ⩽ x ⩽ 0.30) spinels were synthesized by sol–gel route to investigate the influence of V incorporation on the crystal structure, magnetic behaviour, dielectric response, and charge transport mechanisms in CuFe 2 O 4 . X-ray diffraction patterns confirm the formation of single phase tetragonal spinels with I 4 1 /amd symmetry, where increasing V content leads to lattice contraction and a systematic reduction in tetragonality. X-ray photoelectron spectroscopy establishes the presence of Cu 2+ , Fe 3+ /Fe 2+ , and V 3+ cations and indicates that the cation distribution becomes partially inverse, with the degree of inversion varying systematically with V content. Magnetic measurements reveal ferrimagnetic ordering for all compositions, with transition temperature decreasing from 835 K ( x = 0) to 719 K ( x = 0.30) as V 3+ substitution weakens the A–O–B superexchange interactions. A secondary magnetic anomaly associated with Jahn–Teller distortion appears at 659 K in the parent compound ( x = 0) and it decreases gradually upon V substitution. The saturation magnetization exhibits a slight enhancement up to x = 0.10 and then decreases at higher V levels. Dielectric and AC conductivity studies indicate that charge transport is governed predominantly by hopping across Fe 2+ ↔ Fe 3+ ions. V incorporation enhances the dielectric constant and reduces the activation energy for conduction. The temperature variation of frequency exponent suggests a crossover from overlapping large polaron tunnelling at low V concentration to a mixed non-overlapping small polaron tunnelling and correlated barrier hopping mechanism at higher x value. Mott Variable-range hopping analysis further indicates an increased density of localized states and reduced disorder, consistent with improved charge transport.