Colossal Linear Magnetoelectricity in Polar Magnet Fe2Mo3O8

The linear magnetoelectric effect is an attractive phenomenon in condensed matters and provides indispensable technological functionalities. Here a colossal linear magnetoelectric effect with diagonal component ${\ensuremath{\alpha}}_{33}$ reaching up to $\ensuremath{\sim}480\text{ }\text{ }\mathrm{ps}/\mathrm{m}$ is reported in a polar magnet ${\mathrm{Fe}}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$. This effect can persist in a broad range of magnetic field ($\ensuremath{\sim}20\text{ }\text{ }\mathrm{T}$) and is orders of magnitude larger than reported values in literature. Such an exceptional experimental observation can be well reproduced by a theoretical model affirmatively unveiling the vital contributions from the exchange striction, while the sign difference of magnetocrystalline anisotropy can also be reasonably figured out.