Continuous control of local magnetic moment by applied electric field in multiferroicsBa2CoGe2O7

Abstract

Ba 2 CoGe 2 O 7 exhibits a collinear-antiferromagnetic structure with the easy axis along 100 directions and an antiferroelectric order with the polarization axis along the [001] direction. By applying the electric field the magnetic moment rotates from 100 to [110] directions and, simultaneously, the antiferroelectric state changes to the ferroelectric state gradually. This magnetoelectric effect, i.e., continuous control of the local magnetic moment by the electric field, is quantitatively explained by the Hamiltonian including the dielectric energy.

Magnetic Structure and Dielectric State in the Multiferroic Ca2CoSi2O7

“…23) A large single-ion anisotropy D of easy-plane type and a small spin-nematic interaction J p , which is responsible for in-plane anisotropy, play an important role in the material. 25,26) As for the spin dynamics, the large D term induces an optical flat mode, which corresponds to an electric-field active mode confirmed by electromagnetic wave absorption experiments. 27) The spin-nematic interaction is equivalent to the interaction between local electric polarizations, and the dielectric energy was probed in low energy range by an inelastic neutron scattering (INS).…”

“…25,26) The origin of the anisotropy in Ba 2 25) In fact the symmetry of the Ba 2 CoGe 2 O 7 is also lowered by slight lattice distortion 36) and orthorhombic anisotropy in the c-plane is allowed. The spin nematic interaction is, however, dominant and exotic type of spin flop transition was exhibited.…”

“…25) Furthermore, the direction of the magnetic moment in the c-plane was controlled by the electric field, which is quantitatively explained by the Hamiltonian including the dielectric energy estimated from the INS experiment. 26) Here, we focus on an isostructural material Ca 2 CoSi 2 O 7 in order to study physical properties of the material having a different set of D, J p , and additional orthorhombic anisotropy E. The Ca 2 CoSi 2 O 7 has a two-dimensional network of CoO 4 and SiO 4 tetrahedra as shown in Fig. 1(a).…”

Polarization analysis of magnetic excitation in multiferroic Ba2CoGe2O7

“…The multiferroic properties including the electromagnon have been reported in many multiferroics with the cycloidal and proper-screw magnetic structures. Nevertheless multiferroic materials with a collinear structure are rather few [16][17][18] , andåkermanaite compounds A 2 CoB 2 O 7 (A = Ca, Ba, B = Ge, Si) [18][19][20][21][22][23] are the good playground.…”

Switching of Magnons by Electric and Magnetic Fields in Multiferroic Borates

“…In several multiferroics, the coupling between electricity and magnetism is strong enough to allow a mutual influence of both properties. This magnetoelectric coupling has been demonstrated to lead to manipulation of magnetic moments [8][9][10][11][12][13][14] and magnetic structure [15][16][17][18] by external electric field. These effects have been shown to survive up to room temperature [19,20].…”