Fig. 3

a, c The dependence of M_r/M_s of the electric field was measured by sweeping the electric field form + 10 to − 10 kVcm⁻¹ in the [100] and [01-1] directions, respectively. b, d The dependence of M_r/M_s on the electric field was measured by sweeping the electric field from form + 5 to − 5 kVcm⁻¹ in the [100] and [01-1] directions, respectively. The numbers and arrows express the steps and direction of the measurement. And the capital letters in this figure express the values of M_r/M_s at the remnant polarization states