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

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 4f(1) 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 4f(2) 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.