Multiferroic materials exhibit ferroelectric and (anti)ferromagnetic orders simultaneously and show potential applications as new type magnetoelectric sensors, high performance information storages, etc, due to their special magnetoelectric coupling behaviors. Taking advantage of the coexistence, competition, and coupling effects among different orders (such as spin, charge, orbital and lattice), the quantum manipulation of the magnetoelectric properties in multiferroic materials is a brand new method different from the traditional semiconductor microelectronics, which is one of the development trends for new type electronics in post-Moore era. Recently, Postdoctoral Research Sining Dong and Associate Research Yuewei Yin at Xiaoguang Li’s research group in USTC, have achieved important progresses in this area.

Figure 1. Structure scheme, morphology and microstructue images of multiferroic Bi4.2K0.8Fe2O9+δ nanobelts.

Image by DONG Sining et al

In the exploration of new multiferroic materials, Dr. DONG Sining collaborated with Prof. LI Jianqi’s team at institute of physics of CAS, designed and fabricated a new kind of room-temperature multiferroic material Bi4.2K0.8Fe2O9+δ single crystal nanobelts. This material is isostructural with high-temperature superconductor Bi2Sr2CaCu2O8+δ, which is of a novel structure for the multiferroicity. The regular stacking of the BiFeO3-like perovskite blocks and the rock salt slabs along the c axis of the crystal makes the Bi4.2K0.8Fe2O9+δ nanobelts have a natural magnetoelectric–dielectric superlattice structure with a clear magnetoelectric coupling at room temperature. This multiferroic nanomaterial may be helpful for building micro-magnetoelectric devices. The research, entitled “Room temperature multiferroicity in Bi_4.2K_0.8Fe₂O_9+δ”, has been published in Scientific Reports [Sci. Rep. 3, 1245 (2013)].

Dr. Yuewei Yin has made breakthrough in the research on multiferroic prototype device conducted in collaboration with Prof. Qi Li’s research group at Pennsylvania State University, Prof. E. Y. Tsymbal’s group at Universtiy of Nebraska, etc. Based on the multiferroic interfacial magnetoelectric coupling, the researchers designed a special La0.7Sr0.3MnO3/La0.5Ca0.5MnO3/BaTiO3/La0.7Sr0.3MnO3 tunnel junction, for which reversing the ferroelectric polarization of BaTiO3 barrier will modify the hole concentration in La0.5Ca0.5MnO3, change its metallicity between metal and insulator, significantly vary the tunneling parameter, and result in an improvement of tunneling electroresistance effect up two orders of magnitude. Meanwhile, owing to the coexistence of ferromagnetic and ferroelectric properties, the device show four resistance states and allow for greater densities in non-volatile memory. The new method could be used to improve and enhance the functionalities of non-silicon-based electronic devices. The research, entitled “Enhanced Tunnelling Electroresistance Effect due to a Ferroelectrically Induced Phase Transition at a Magnetic Complex Oxide Interface”, has been published in Nature Materials journal [Nature Materials 12, 397 (2013)].

Figure 2. Schematic illustration of the multiferroic tunnel junction of two polarization configurations.

Image by YIN Yuewei et al

The researches were supported by National Natural Science Foundation of China and Ministry of Science and Technology of China.

 

Paper link:

http://www.nature.com/srep/2013/130213/srep01245/full/srep01245.html

http://www.nature.com/doifinder/10.1038/nmat3564

 

(DONG Sining,YIN Yuewei,School of Physical Sciences)