Magnetoelectric coupling induced by Jahn–Teller Cu2+ in SrFe12O19 ceramics

Abstract

Direct magnetoelectric (ME) coupling between magnetic and ferroelectric orders can be realized in spiral magnets. In this work, Jahn–Teller Cu²⁺ ions and Ti⁴⁺ ions were introduced in SrFe₁₂O₁₉ to destroy the collinear magnetic structure. It is found that Cu²⁺ ions mainly enter into the 2a and 4f₁ sites of the spinel block, causing local enhanced Dzyaloshinskii–Moriya (DM) interaction and lattice distortion and therefore resulting in the appearance of conical spin order. Ti⁴⁺ ions at 4f₂ and 2b sites also induce a local uncompensated D vector and benefit the formation of conical spin order, while their non-magnetic nature hinders the spin propagation. Based on the proposed DM interaction model, the Jahn–Teller distortion and d–p hybridization mechanism were considered to be responsible for the enhanced ME effect. The present results highlight the role of the Jahn–Teller effect in the induction of conical spin order in M-type hexaferrite and the enhancement of ME coupling.