MAGNETOELECTRIC

Magnetoelectric effect

Free energy of magnetoelectric system:

The linear responses obtained from the free energy are:

W. F. Brown et al., Phys. Rev. 168, 574 (1968)

ITC, Vol. D, p. 137Time reversal symmetry

breaking, T(t -t)

Inversion symmetry breaking, I (x -x) IT(x -x,t -t)

is conserved

linear magnetoelectric CONSTRAINED

Linear Magnetoelectric in Cr2O3

300

G.T. Rado and V.J.Folen, PRL 6, 607 (1961), J. Appl. Phys 33, 1126 (1962)

anisotropicTN = 306 K

Magnetoelectric effect in multiferroic

Multiferroic: coexistance between : (magnetic, electric and strain) order parameter

PHYSICS TODAY Oct 2010

Magnetoelectric coupling

Quadratic MEC

Linear MEC

MnTiO3

Y(Mn,Ga)O3

SOME OF MAGNETOELECTRIC MATERIALS

more....

magnetism: unfilled d/f -shell: Mn3+, Fe3+,Co3+,Ni3+, rare earthsferroelectrics: empty d-shells: Ti4+, Zr4+, Nb5+, W6+, rare earths

lone pair: Pb2+,Bi3+

IMPORTANCE OF MULTIFERROICS

T. Kimura et al, Nature 426, 55 (2003)

MULTIFERROIC TbMnO33

T. Kimura et al, Nature 426, 55 (2003)

Magnetic control of ferroelectric polarization

M. Kenzelmann et al., PRL 95, 087206 (2005)

Spin Density Wave

M. Mostovoy, PRL 96, 067601 (2006)

Spiral magnetic phase driven ferroelectricity

POLARIZATION FLOP

RMnO3

FERROELECTRICITY IN SPIN HELIX

POLARIZATION REVERSAL UPON MAGNETIZATION REVERSAL

Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17