Observation of Magnetoelectric Multiferroicity in a Cubic Perovskite System: ${\mathrm{LaMn}}_3{\mathrm{Cr}}_4{\mathrm{O}}_{12}$

Magnetoelectric multiferroicity is not expected to occur in a cubic perovskite system because of the high structural symmetry. By versatile measurements in magnetization, dielectric constant, electric polarization, neutron and x-ray diffraction, Raman scattering, as well as theoretical calculations, we reveal that the $A$-site ordered perovskite $\mathrm{La}{\mathrm{Mn}}_3{\mathrm{Cr}}_4{\mathrm{O}}_{12}$ with cubic symmetry is a novel spin-driven multiferroic system with strong magnetoelectric coupling effects. When a magnetic field is applied in parallel (perpendicular) to an electric field, the ferroelectric polarization can be enhanced (suppressed) significantly. The unique multiferroic phenomenon observed in this cubic perovskite cannot be understood by conventional spin-driven microscopic mechanisms. Instead, a nontrivial effect involving the interactions between two magnetic sublattices is likely to play a crucial role.

Figure 1

(a) Schematics of crystal structure of LMCO with space group $Im\text{−}3$. (b) NPD patterns at selected temperatures. The indexed (111) and (100) peaks arise from the AFM ordering of the $B$-site Cr sublattice and the $A^{\prime }$-site Mn sublattice, respectively. (c),(d) Temperature dependence of the integrated NPD intensities of (111) and (100) peaks, respectively. (e),(f) $G$-type AFM structure of the $B$-site Cr sublattice and the $A^{\prime }$-site Mn sublattice with spin orientation along the [111] direction, respectively. (g) A complete set of spin alignment composed of Cr and Mn spins below $T_{\mathrm{Mn}}$. For clarity, La and O atoms are omitted in the structures. Blue ball, Cr atom; red ball, Mn atom.

Figure 2

Temperature dependence of (a) dielectric constant $ϵ$ and magnetic susceptibility $\chi$, (b) pyroelectric current $I_p$, and (c) ferroelectric polarization $P$ in both $+\text{Poled}$ and $-\text{Poled}$ conditions. $ϵ$ and $I_p$ were measured without magnetic field. The insets of (b) and (c) show the enlarged views near 50 K.

Figure 3

(a) Temperature dependence of $I_p$ and (b) the difference of polarization $\mathrm{\Delta }P$ at different poling conditions and different magnetic fields below 50 K. (c),(d) Temperature dependence of $ϵ$ measured at 1 MHz and different magnetic fields with $H\parallel E$ and $H\perp E$ configurations, respectively. The data have been shifted for clarity.