Abstract
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 PbTiO3 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 PbTiO3 nanodots exhibit unconventional multiferroic phase transitions. The nanosize and nonstoichiometric effects intrinsic to nanodots bring about the coexistence of ferromagnetism with the host electric polarization, mediated by the termination and surface morphology. We also predict the key features of the size-dependent phase diagram of nanodots that involve a rich sequence of ferroelectric-multiferroic-ferromagnetic/nonmagnetic (FE-MF-FM/NM) multiferroic phase transitions. The present work thus provides an avenue to realizing multiferroics and multifunctional oxides in low-dimensional systems.
Highlights
The pursuit of unusual phases and their correlated transitions is at the very core of condensed matter science
As the size of perovskite ferroelectric oxides approaches the nanometer scale, they suffer from remarkable size and surface effects that manifest themselves in marked deviation of their physical properties from those of their bulk counterparts, such as a decrease in remnant polarization and coercive field, modification of phase transition temperature and domain dynamics[21,22]
We report that PbTiO3 nanodots exhibit unusual multiferroic phases with coupled ferroelectricity and ferromagnetism based on first-principles calculations
Summary
Nanodots received: 29 November 2016 accepted: 22 February 2017 Published: 03 April 2017. 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. Typical ferroelectrics such as PbTiO3 exhibit diverse phase transition sequences, the conventional incompatible mechanisms of ferroelectricity and magnetism keep them as nonmagnetic phases, despite the immense practical prospective of multiferroics in novel functional devices. There have been significant efforts in the search for new multiferroic materials in perovskite oxides[7,8,9,10,11,12], intrinsic multiferroelectric phases remain largely elusive[13] The scarcity of such multiferroelectrics is closely related to the violation of the conventional mechanism of cation off-centering for the formation of an electric dipole, which commonly requires an empty d0 electronic configuration, and the formation of magnetism due to partially filled d orbitals. This work provides a novel pathway to multiferroic transitions in conventional nonmagnetic ferroelectrics
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