Asymmetry in Standard model: Experimentally obtained:

Výzkum a praktické využití magnetických feroelektrik Stanislav Kamba Fyzikální ústav AVČR, Na Slovance 2, Praha 8 Multiferoika jsou materiály, ve kterých koexistují dvě a více feroických vlastností. Ferroelectric Ferrotoroidic Ferroelastic Ferromagnetic

Bibes & Barthélémy, Nature Materials, 7, 425 (2008) Chen et al. APL 89, (2006) Sketch of MERAM element

M. Gajek et al. Nature Materials, 6, 296 (2007) La 0.1 Bi 0.9 MnO 3 magnetoferroelectrics, 2 nm thin film Tunnel junctions with multiferroic barriers M  || M  M  || M 

Béa et al. JPCM 20, (2008) Fiebig, J. Phys. D: Appl. Phys. 38, R123 (2005) Classification of insulating oxides

Multiferroics with spiral magnetic structure TbMnO 3, T N =40 K, T C =27 K Kimura et al. Nature 426, 55 (2003) T. Kimura Annu. Rev. Mater. Res. 37, 387 (2007 )

Different types of multiferroics •Type-II: Magnetically driven multiferroics, T C < T N a)Multiferroics with spiral magnetic structure The inverse Dzyaloshinskii-Moriya mechanism  - constant proportional to the spin orbit coupling and superexchange interaction e ij – unit vector connecting the neighboring i and j sites b) Multiferroics with collinear magnetic structure Symmetric (S i.S j )- type interaction, termed (super)exchange striction H. Kimura et al. J. Phys. Soc. Jpn. 75, (2006 ) T. Kimura Annu. Rev. Mater. Res. 37, 387 (2007 )

Strain induced ferroelectricity and ferromagnetism in tensile strained EuTiO 3 /DyScO 3 Lee et al. Nature 466, 954 (2010)FZÚ AVČR;

Strain-induced ferroelectric phase transition in EuTiO 3 /DyScO 3 +1% tensile strain Lee et al. Nature 466, 954 (2010) P S  30  C/cm 2 Nature 476, 114 (2011)

Strain induced ferromagnetism in tensile strained EuTiO 3 /DyScO 3 Lee et al. Nature 466, 954 (2010)

Magnetic dependence of TO1 phonon frequencyEuTiO 3 / LSAT Kamba et al. PRB 85, (2012)

Comples THz spectra of YMnO 3 single crystal Kadlec et al. PRB 84, (2011)

Predictions for the EDM magnitude of electrone

• d = a s; switching the electric dipole moment switches the spin moment •Material property requirements: –Ferroelectric, switchable at few K, large polarization –Magnetic, but not ordered at a few K –Macroscopic sample (around 1 cm) –A low temperature multiferroic! Electron with an electric dipole moment K.Z. Rushchanskii et al., Nature Materials, 9, 649(2010) switch d with E or switch s with H

EuTiO 3 T N =7 K paraelectric a=3.9 Å BaTiO 3 ferroelectric a=4.0 Å (Eu,Ba)TiO 3

Dielectric and magnetic properties of Eu 0.5 Ba 0.5 TiO 3 Cubic Pm3mOrthorhombic Amm2 T C =215 KT N =1.9 KT Rushchankii et al., Nature Materials, 9, 649 (2010) V. Goian et al. JPCM 23, (2011) S. Kamba, Čs. čas. fyz. 60, 329 (2010)

„THz mezera” kilo mega giga tera peta exa zetta yotta radiové vlny mikro- vlny nízké frekvence viditelnértg. záření gamma ELEKTRONIKA OPTIKA frekvence [Hz] „tradiční“ zdroje – příliš slabé:  Při frekvencích > 10 GHz klesá účinnost obvodů: elektrony nestačí sledovat rychlé změny elmg. pole Při frekvencích < 10 THz optické zdroje září málo vlnová délka 1000 km 1 km 1 m 1 mm 1 μ m 1 nm 1 pm 1 fm Infrač. UV Elekromagnetické spektrum FZÚ AVČR;

I.3. Dielectric spectrum Dielectric spectrum – a sum of the dielectric dispersion regions A set of the frequency - temperature dependences should be studied FZÚ AVČR;

THz laboratoř FZÚ AVČR;

Magnetický kryostat v THz laboratoři FZÚ AVČR;

Infračervená laboratoř FZÚ AVČR;