Multiferroic Phases and Transitions in Ferroelectric Lead Titanate Nanodots.

Discovery of novel phases and their associated transitions in low-dimensional nanoscale systems is of central interest as the origin of emergent phenomena and new device paradigms. Although typical ferroelectrics such as PbTiO exhibit diverse phase transition sequences, the conventional incompatible mechanisms of ferroelectricity and magnetism keep them as simply nonmagnetic phases, despite the immense practical prospective of multiferroics in novel functional devices. Here, we demonstrate using density function theory that PbTiO nanodots exhibit unconventional multiferroic phase transitions.

Unusual Multiferroic Phase Transitions in PbTiO Nanowires.

Unconventional phases and their transitions in nanoscale systems are recognized as an intriguing avenue for both unique physical properties and novel technological paradigms. Although the multiferroic phase has attracted considerable attention due to the coexistence and cross-coupling of electric and magnetic order parameters, mutually exclusive mechanism between ferroelectricity and ferromagnetism leaves conventional ferroelectrics such as PbTiO simply nonmagnetic. Here, we demonstrate from first-principles that ultrathin PbTiO nanowires exhibit unconventional multiferroic phases with emerging ferromagnetism and coexisting ferroelectric/ferrotoroidic ordering.

Multiferroic grain boundaries in oxygen-deficient ferroelectric lead titanate.

Ultimately thin multiferroics arouse remarkable interest, motivated by the diverse utility of coexisting ferroelectric and (anti)ferromagnetic order parameters for novel functional device paradigms. However, the ferroic order is inevitably destroyed below a critical size of several nanometers. Here, we demonstrate a new path toward realization of atomically thin multiferroic monolayers while resolving a controversial origin for unexpected "dilute ferromagnetism" emerged in nanocrystals of nonmagnetic ferroelectrics PbTiO3.