Multiferroic and magnetoelectric materials -Developments and perspectives

Multiferroic (MF) materials with simultaneous magnetic and electric long range order and occasionally, mutual magnetoelectric (ME) coupling, have recently attracted considerable interest. The small linear ME effect has been shown to control spintronic devices very efficiently, e. g. via the classic ME antiferromagnet Cr2O3 using exchange bias. Similar nano-engineering concepts exist also for type-I MF single phase materials, whose magnetic and polar orders have distinct origins like BiFeO3. Strong ME coupling occurs in type-II multiferroics, where ferroelectricity is due to spiral spin order as in TbMnO3. Record high ME response coming close to applicability arises in stress-strain coupled multiphase magnetoelectrics such as PZT/FeBSiC composites. Higher order ME response in disordered systems (type-III multiferroics) extends the conventional MF scenario toward ME quantum paraelectric and multiglass materials with polarization-induced control of magnetic exchange, as e. g. in EuTiO3, Sr0.98Mn0.02TiO3, and PbFe0.5Nb0.5O3.