Electrically switchable large near-infrared optical diode effect in an iron-based oxide

We report a large near-infrared (NIR) optical diode effect (ODE) and its electric field switching in the antiferromagnetic state of ${\mathrm{LiFePO}}_{4}$. The difference in absorption coefficients for light travelling in opposite directions, divided by the sum, reaches $\ensuremath{\sim}25%$ at a photon energy of 1.18 eV. Symmetry analysis attributes the ODE to the spin-allowed $d\text{\ensuremath{-}}d$ transitions of octahedrally coordinated $\mathrm{F}{\mathrm{e}}^{2+}$ via the spin-orbit interaction. Given the abundance of iron and potentially high magnetic transition temperature in iron-based materials, this study may open the door to the application of the NIR ODE.