Jahn–Teller effect driven dielectric anomaly and intrinsic magnetodielectric behaviors in nickel chromate

Abstract

Some spinel chromium oxides with the chemical formula ACr2O4 exhibit magnetic-induced multiferroicity due to the special spiral spin order. However, because of the relatively low temperature of the ordered spiral phase, this kind of multiferroicity generally displays a limited coexistence of magnetic and ferroelectric orders in a narrow temperature range. The Jahn–Teller (JT) effect, serving as a crucial link between charge and orbit degrees of freedom, can facilitate efficient modulation of multiferroic properties. In this work, Ni1−xCuxCr2O4 (0 ≤ x ≤ 0.2) series are synthesized by occupying the same Wyckoff site with two kinds of JT ions. The microstructure and JT distortion can be distinctly influenced by varying the doping level of Cu2+ ions. Particularly, Ni0.85Cu0.15Cr2O4 (x = 0.15) presents the pronounced JT distortion, accompanied by observation of dielectric anomaly at ∼78 K, resulting from spin–orbit coupling. This implies that the JT effect can significantly promote the contribution of spin–orbit coupling in magnetoelectric correlation. Moreover, the magnetodielectric effect induced by intrinsic magnetoelectric coupling is confirmed in Ni0.85Cu0.15Cr2O4 over a wide temperature range of 10–200 K, which is much higher than the Néel temperature of ∼85 K. It indicates that spin–orbit coupling based on the JT effect could overcome the constraint of magnetic order to achieve effective control on electric polarization performance under an applied magnetic field, thereby showing broad application prospects.