Control of ferroelectric phase by chemical pressure in (Gd, Tb)MnO/sub 3/ crystals

We have investigated the dielectric properties of Gd/sub 1-x/Tb/sub x/MnO/sub 3/ crystals in magnetic fields to clarify the crossover between two distinct ferroelectric phases, GdMnO/sub 3/-type (first-order displacive) and TbMnO/sub 3/-type (second-order order-disorder). We have found that the compositional phase boundary between the phases exists around 0.3