Critical scaling analysis for displacive-type organic ferroelectrics around ferroelectric transition

The critical scaling properties of displacive-type organic ferroelectrics, in which the ferroelectric-paraelectric transition is induced by spin-Peierls instability, are investigated by Green's function theory through the modified Arrott plot, critical isothermal and electrocaloric effect (ECE) analysis around the transition temperature TC. It is shown that the electric entropy change −ΔS follows a power-law dependence of electric field E:−ΔS∼En with n satisfying the Franco equation n(TC)=1+(β−1)/(β+γ)=0.618, wherein the obtained critical exponents β=0.440 and γ=1.030 are not only corroborated by Kouvel-Fisher method, but also confirm the Widom critical relation δ=1+γ/β. The self-consistency and reliability of the obtained critical exponents are further verified by the scaling equations. Additionally, a universal curve of −ΔS is constructed with rescaling temperature and electric field, so that one can extrapolate the ECE in a certain temperature and electric field range, which would be helpful in designing controlled electric refrigeration devices.