ACr2O4 syetem allows one to analyze the interplay of lattice, charge, orbital, and spin degrees of freedom. However, very few materials have been studied from the viewpoint of the coupling between frustration and Jahn-Teller effects by changing the orbital configuration of B-site cation. Hence, Fe1+xCr2-xO4 is a remarkable compound. In our early work, we constructed the complicated T - x phase diagram of the lattice and magnetic structures. The Cr3+ ions always stay at the B site and the only electron transfer should be between Fe2+ and Fe3+ ions. We also observe some interesting phenomena with the magnetoelasticity, ferroelectricity and magnetodielectricity. In order to elucidate the interaction between the spin and lattice degrees of freedom, it is very interesting to study the details of the static structure and dynamic response of these compounds.