Giant enhancement of the magnetization in the BiFeO3-CoFe2O4
heteroepitaxial nanostructure
Ying-Jiun Chen1, Ying-Hui Hsieh2, Chang-Yang Kuo1, Meng-Jie Huang1,
Chih Yu Hua1, Chien-Yi Li, Wei-Cheng Kuo2, Jan-Chi Yang2, Fan-Hsin
Chang1, Huang-Ming Tsai1, Wei-Jyun Yu1, Wei-Chang Wang1, Yi-Ying
Chin1, Ying-Hao Chu2, Hong-Ji Lin1, and Chien-Te Chen1
1
National Synchrotron Radiation Research Center, Hsinchu 30010, Taiwan
2
Department of Materials Science and Engineering, National Chiao Tung University,
Hsinchu 30010, Taiwan
Exotic physical phenomena emerge in complex correlated oxides because the
coupling between lattice, charge, orbital, and spin degrees of freedom undergoes the
competition and cooperation with subtle energy balance [1]. Furthermore, when two
complex oxides are brought together, heterointerfaces trigger a host of novel
phenomena and provide a powerful route to tune these degrees of freedom. By
manipulating the crystal orientations with different substrates, the constituent
materials via interface engineering play an emphatic role in generating unique types
of magnetoelectric coupling [2].
In this work, the coexistence of strong magnetoelectric coupling, stable
ferrielectric and ferroelectrics is achieved when CoFe2O4 nanorods are embedded in a
self-organized way within a BiFeO3 matrix. By generating a unique XMCD signature,
the site distribution of the Co2+ at Oh, Fe3+ at Oh and Fe3+ at Td sites in the BiFeO3CoFe2O4, SrTiO3-CoFe2O4 and CoFe2O4 thin film on STO substrates can be observed.
XMCD signal at the Co-L3 edge in BiFeO3-CoFe2O4 heterostructure reaches to ~40%
and is approximately three times larger than that in CFO/STO (14.0%) thin film and
STO-CFO (14.6%), in good agreement with the SQUID measurement. The
considerably large magnetic enhancement of the vertical heterointerfaces provide
quantitative evidences of existence of the novel states at the oxide interfaces, and
possibility to manipulate multiferroic properties as well as the spin and orbital
configurations at the interface. Such vertical nanocomposites engineering of
magnetoelectric and local giant magnetic enhancement might achieve
multi-application for next-generation and low-energy consumption spintronics.
[1] Y. Tokura and N. Nagaosa, Science, 288, 462 (2000).
[2] S. C. Liao, P. Y. Tsai, C. W. Liang, H. J. Liu, J. C. Yang, S. J. Lin, C. H. Lai, and
Y. H. Chu, ACS Nano, 5,4118 (2011).