Low-field magnetoelectric effect at room temperature.

The discoveries of gigantic ferroelectric polarization in BiFeO(3) (ref. 1) and ferroelectricity accompanied by a magnetic order in TbMnO(3) (ref. 2) have renewed interest in research on magnetoelectric multiferroics, materials in which magnetic and ferroelectric orders coexist, from both fundamental and technological points of view. Among several different types of magnetoelectric multiferroic, magnetically induced ferroelectrics in which ferroelectricity is induced by complex magnetic orders, such as spiral orders, exhibit giant magnetoelectric effects, remarkable changes in electric polarization in response to a magnetic field. Many magnetically induced ferroelectrics showing the magnetoelectric effects have been found in the past several years. From a practical point of view, however, their magnetoelectric effects are useless because they operate only far below room temperature (for example, 28 K in TbMnO(3) (ref. 2) and 230 K in CuO (ref. 11)). Furthermore, in most of them, the operating magnetic field is an order of tesla that is too high for practical applications. Here we report materials, Z-type hexaferrites, overcoming these problems on magnetically induced ferroelectrics. The best magnetoelectric properties were obtained for Sr(3)Co(2)Fe(24)O(41) ceramics sintered in oxygen, which exhibit a low-field magnetoelectric effect at room temperature. Our result represents an important step towards practical device applications using the magnetoelectric effects.

[1]  C. F. Cook,et al.  Crystallography of the Hexagonal Ferrites , 1971, Science.

[2]  A. Deriu,et al.  Sublattice magnetization and anisotropy properties of Ba3Co2Fe24O41 hexagonal ferrite , 1976 .

[3]  Hans Schmid,et al.  Multi-ferroic magnetoelectrics , 1994 .

[4]  O. Kimura,et al.  Enhanced Dispersion Frequency of Hot‐Pressed Z‐Type Magnetoplumbite Ferrite with the Composition 2CoO·3Ba0.5Sr0.5O·10.8Fe2O3 , 1995 .

[5]  Nicola A. Hill,et al.  Why Are There so Few Magnetic Ferroelectrics , 2000 .

[6]  R. Pullar,et al.  The synthesis and characterization of the hexagonal Z ferrite, Sr3Co2Fe24O41, from a sol-gel precursor , 2001 .

[7]  Y. Tokura,et al.  Magnetic control of ferroelectric polarization , 2003, Nature.

[8]  T. Tachibana,et al.  X-ray and neutron diffraction studies on iron-substituted Z-type hexagonal barium ferrite: Ba3Co2−xFe24+xO41 (x=0–0.6) , 2003 .

[9]  Akhlesh Lakhtakia,et al.  Introduction to Complex Mediums for Optics and Electromagnetics , 2003 .

[10]  R. Ramesh,et al.  Epitaxial BiFeO3 Multiferroic Thin Film Heterostructures , 2003, Science.

[11]  T. Tachibana,et al.  Estimation of Magnetic Structures of Z-type Ferrites: (Ba, Sr)3Co2Fe24O41 by Neutron Diffraction , 2003 .

[12]  T. Kimura,et al.  Electric polarization rotation in a hexaferrite with long-wavelength magnetic structures. , 2005, Physical review letters.

[13]  C. L. Zhang,et al.  Magnetic inversion symmetry breaking and ferroelectricity in TbMnO3. , 2005, Physical review letters.

[14]  N. Nagaosa,et al.  Spin current and magnetoelectric effect in noncollinear magnets. , 2004, Physical review letters.

[15]  Manfred Fiebig.  Revival of the Magnetoelectric Effect , 2005 .

[16]  T. Tachibana,et al.  Crystal and magnetic structures and their temperature dependence of Co2Z-type hexaferrite (Ba,Sr)3Co2Fe24O41 by high-temperature neutron diffraction , 2006 .

[17]  Maxim Mostovoy,et al.  Ferroelectricity in spiral magnets. , 2005, Physical review letters.

[18]  E. Dagotto,et al.  Role of the Dzyaloshinskii-Moriya interaction in multiferroic perovskites , 2005, cond-mat/0508075.

[19]  N. Mathur,et al.  Multiferroic and magnetoelectric materials , 2006, Nature.

[20]  Tsuyoshi Kimura,et al.  Spiral Magnets as Magnetoelectrics , 2007 .

[21]  N. Momozawa,et al.  Superexchange Interactions of (Ba1-xSrx)2Zn2Fe12O22 System Studied by Neutron Diffraction , 2007 .

[22]  S. Cheong,et al.  Multiferroics: a magnetic twist for ferroelectricity. , 2007, Nature materials.

[23]  T. Kimura,et al.  Cupric oxide as an induced-multiferroic with high-TC. , 2008, Nature materials.

[24]  Y. Tokura,et al.  Low-Magnetic-Field Control of Electric Polarization Vector in a Helimagnet , 2008, Science.

[25]  T. Arima,et al.  Ferroelectric Polarization Reversal by a Magnetic Field in Multiferroic Y-type Hexaferrite Ba2Mg2Fe12O22 , 2008 .

[26]  D. Khomskii,et al.  Classifying multiferroics: Mechanisms and effects , 2009 .

[27]  S. Y. Haam,et al.  Realization of giant magnetoelectricity in helimagnets. , 2010, Physical review letters.