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Seminar/Colloquim

PHYSICS/BK21 SEMINAR[4.9]

본문

 

[ 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 )  

 

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