Pressemeldung: Single-domain multiferroic BiFeO3 films

21. September 2016

Multiferroic are the materials which exhibit more than one order parameter simultaneously. Coexisting order parameters and inherent couplings in multiferroics form a potent playground to obtain new functionalities for an electrical stimulus. In spintronics, for example, multiferroic can be used as block layer in spin valves, with the aim of electrically controlling the giant magnetoresistance via the magnetoelectric coupling. Among the numerous multiferroic systems, BiFeO3 (BFO) is the most promising and well studied.

BFO exhibits large ferroelectric polarization (P) and G-type antiferromagnetism with high transition temperatures, making it appealing for applications in nonvolatile logic and memory devices. However, BFO thin films reported mostly have multidomain on both P and antiferromagnetic (AFM) axes. The multi-domain nature of the material tends to nullify the properties of interest and complicates the thorough understanding of the mechanisms that are responsible for those properties. For the real applications, it is necessary to create films with a single domain and well defined parameters for both the magnetic and ferroelectric orders.

To this aim, we collaborate with National Synchrotron Radiation Research Center (NSRRC) and National Chiao Tung University (NCTU) in Taiwan as well as Oak Ridge National Laboratory in Unite State to explore a route to create the single-domain multiferroic BFO film. We have successfully fabricated a single multiferroic domain BFO film, which has a single AFM axis parallel to b-axis and a single P towards c-axis as well as a canted ferromagnetic along a-axis. Furthermore, this single-domain multiferroic BFO film can be embedded into a ferromagnetism (FM)/BFO heterostructure to give the spin in the FM layer a preferred direction for the entire film. Our next goal is to realize the electrical control of the FM moment of this ferromagnetic-like multiferroic heterostructure. We believe that this single multiferroic domain BFO film has large potential as a playground to engineer novel multifunctional devices.

CYK, ZH, LHT, YHC / CPfS

Schematic of magnetization and ferroelectric polarization axes for a hetero structure consisting of a Co metal film grown on a single domain BFO film.

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