PHYSICS/BK21 SEMINAR[4.9]

[ Multiferroics - Control of Physical Properties by Electric Field ]

  * Speaker : Dr. Chan-Ho Yang [Department of Physics, KAIST]

  * Place  : Physics Seminar Room (Science Bldg, 3-201)

  * Date & Time : Apr, 9 (Fri)  4:00 ~ 5:00 pm

 l  Abstract

 The magnetoelectric effect that refers to the inter-coupling phenomena between electric and magnetic degrees of freedom has been extensively studied in the complex-oxide community since large effects were discovered in single compound materials [1, 2]. Especially, bismuth ferrite, BiFeO₃ has received a lot of attention due to its multiferroic properties – the coexistence of ferroelectricity and magnetism – at room temperature. Here we will introduce our concepts to find viable routes to magnetoelectric applications and discuss possible issues from a practical point of view. In addition to the magnetoelectric issues, continuing attention on this compound is expected regarding electronic conduction, photovoltaic effect, and a highly-strained phase of BiFeO₃ stabilized by heteroepitaxial growth. Observations of a colossal electro-strain induced by phase competition between two isostructural BiFeO₃ phases, i.e, the normal rhombohedral-like phase and the highly-strained tetragonal-like phase, will stimulate more vigorous study of this compound [3]. Finally it will be presented that electronic conduction in doped BiFeO₃ films can be modulated by orders of magnitude in an electric way. Using electric fields, we have been able to create, erase, and invert p-n junctions in calcium doped BiFeO₃ films [4]. The underlying mechanism will be discussed on the basis of interplay between ionic movement of oxygen vacancies and electronic conduction.  

[1] S-W. Cheong and M. Mostovoy, Nature Mater. 6, 13–20 (2007). 

[2] R. Ramesh and N. A. Spaldin, Nature Mater. 6, 21–29 (2007).

[3] R. J. Zeches et al., Science 326, 977-980 (2009).

[4] C.-H. Yang et al., Nature Mater. 8, 485-493 (2009).

Contact Person : Prof. Yoon Hee JEONG (054-279-2078, yhj@postech.ac.kr )