New Multiferroic Materials from Building Blocks

multiferroic materials
Figure. A chemical design strategy for creating artificial multiferroics using oxide nanosheets.

A research group led by principal investigator Minoru Osada and fellow Takayoshi Sasaki, International Center for Materials Nanoarchitectonics (MANA), NIMS, successfully developed room temperature multiferroic materials by a layer-by-layer assembly of nanosheet building blocks. Multiferroic materials are expected to play a vital role in the development of next-generation multifunctional electronic devices.

The design of new multiferroics, or materials that display both ferroelectricity and ferromagnetism, is of fundamental importance for new electronic technologies. However, the co-existence of ferroelectricity and magnetic order at room temperature in single compounds is rare, and heterostructures with such multiferroic properties have only been made with complex techniques (such as pulsed-laser deposition and molecular beam epitaxy).

Seeking to develop room-temperature multiferroics, the research group utilized a new chemical design for artificial multiferroic thin films using two-dimensional oxide nanosheets as building blocks (see figure). This approach enables engineering the interlayer coupling between the ferromagnetic and ferroelectric orders, as demonstrated by artificial superlattices composed of ferromagnetic Ti0.8Co0.2O2nanosheets and dielectric perovskite-structured Ca2Nb3O10 nanosheets. The (Ti0.8Co0.2O2/Ca2Nb3O10/Ti0.8Co0.2O2) superlattices exhibit the multiferroic effects at room temperature, which can be modulated by tuning the interlayer coupling (i.e., the stacking sequence).

This study opens a pathway to create new artificial materials with tailored multiferroic properties. In addition, the successful development of room temperature multiferroic nanofilms may lead to their application to new memory devices, taking advantage of their multifunctionality and low-voltage operation.