Poling procedure dependence of electric behaviors below T_Mn. (a) Temperature dependence of pyroelectric current I_p by+ poled and –poled under 200–75 K and 75–30 K poling conditions. Temperature dependence of (b) I_p and (c) the difference of polarization δP (= P(T)-P(50 K)) after being+ poled from 200 K down to the selected temperatures. The δP is obtained by integration of I_p in panel (b) as a function of time. As shown in panel (b), a dip-peak feature is observed when E passes through both 180 K and T_Mn, whereas only a single dip is observed when E is turned off at temperatures higher than T_Mn. Therefore, the dip in I_p at T_Mn must be contributed by the FE2 phase, and the peak in I_p at T_Mn originates from the FE1 phase. The corresponding negative δ P indicates that electric polarization of the FE2 phase decreases in magnitude below T_Mn.