Ferromagnetism and orbital order in a topological ferroelectric

TL;DR

This study demonstrates that vanadium doping in a layered ferroelectric material induces robust ferromagnetism and preserves electric polarization, offering a novel pathway to multiferroic materials with potential applications in spintronics.

Contribution

It reveals that magnetic doping can induce multiferroicity in a topological ferroelectric without destroying its polarization, highlighting an unconventional mechanism involving orbital order.

Findings

Vanadium doping preserves electric polarization.

Doped material exhibits robust ferromagnetism.

Dopants tend to cluster into chains, affecting electronic properties.

Abstract

We explore via density functional calculations the magnetic doping of a topological ferroelectric as an unconventional route to multiferroicity. Vanadium doping of the layered perovskite La$_{2}$Ti$_{2}$O$_{7}$ largely preserves electric polarization and produces robust ferromagnetic order, hence proper multiferroicity. The marked tendency of dopants to cluster into chains results in an insulating character at generic doping. Ferromagnetism stems from the symmetry breaking of the multi-orbital V system via an unusual "antiferro"-orbital order, and from the host's low-symmetry layered structure.