Photomagnetoelectric and magnetophotovoltaic effects in multiferroic ${\mathrm{BiFeO}}_3$

A polarized light beam modifies the equilibrium tensors associated with any measurable property of a crystal. The light-induced linear magnetoelectric susceptibility and electric current density of bismuth ferrite (BFO) are investigated theoretically using their expansion in Wigner spherical functions. Under illumination, the interplay between magnetoelectric and photovoltaic properties yields the emergence in the paramagnetic and multiferroic phases of BFO of linear photomagnetoelectric tensor components changing sign in domains with opposite electric polarization or magnetization, and to magnetophotocurrents changing sense in opposite ferroelectric and magnetic domains.

Figure 1

(a) Spherical coordinates (α,β,γ) describing the orientation of the electromagnetic frame (e,b,k) with respect to the laboratory frame (x,y,z). Here, e and b represent the wave amplitude, and k its wave vector. (b) Cartesian coordinates of the BFO crystal with $z$ along the threefold axis and $x$ along the [110] hexagonal axis normal to the (y,z) plane involved in the $m{1}^{\prime }$ symmetry of the multiferroic phase. Fe atoms are located at the vertices of the tripled hexagonal cell.

Figure 2

Orientation of the light-induced photocurrents j, assuming positive coefficients in Eqs. (6) and (7), in two neighboring ferroelectric domains with opposite electric polarizations $\pm {\mathbf{P}}_0$ in (a) the paramagnetic and (b) the multiferroic phases of BFO. The orientations of j for k parallel or normal to the $z$ axis are discussed in the text.

Figure 3

Orientation under applied magnetic field $H^Z$ of light-induced magnetophotocurrents in two neighboring ferroelectric or magnetic domains of BFO with opposite electric polarization $\pm {\mathbf{P}}_0$ or magnetization $\pm {\mathbf{M}}_0$, assuming positive coefficients in Eqs. (8) and (9). (a) and (b) correspond to the paramagnetic and multiferroic phases of BFO, respectively. The orientations of $\mathbf{j}\left(0\right),\mathbf{j}\left(1\right),\mathbf{j}\left(2\right),\mathbf{j}\left(3\right)$ for k parallel or normal to the $z$ axis are discussed in the text.