Coupling of magnetic and ferroelectric hysteresis by a multi-component   magnetic structure in Mn2GeO4
  The olivine compound Mn2GeO4 is shown to feature both a ferroelectric polarization and a ferromagnetic magnetization that are directly coupled and point along the same direction. We show that a spin spiral generates ferroelectricity (FE), and a canted commensurate order leads to weak ferromagnetism (FM). Symmetry suggests that the direct coupling between the FM and FE is mediated by Dzyaloshinskii-Moriya interactions that exist only in the ferroelectric phase, controlling both the sense of the spiral rotation and the canting of the commensurate structure. Our study demonstrates how multi-component magnetic structures found in magnetically-frustrated materials like Mn2GeO4 provide a new route towards functional materials that exhibit coupled FM and FE. 
J. S. White, T. Honda, K. Kimura, T. Kimura, Ch. Niedermayer, O.   Zaharko, A. Poole, B. Roessli, M. Kenzelmann
cond-mat.mtrl-sci cond-mat.other