Domain structure, local hysteresis and ferroelectric phase transition in (CH₃NH₃)₅Bi₂Br₁₁ (MAPBBB) single crystals

Local ferroelectric properties of single crystals (CH 3 NH 3 ) 5 Bi 2 Br 11 (MAPBB) are investigated by Scanning Probe Microscopy (SPM) in a piezoelectric contact mode. The SPM signal proportional to the effective piezoelectric coefficient, d eff , is measured along with the standard topography. Both ferroelectric domain imaging and local hysteresis measurements are performed at room temperature in the close vicinity of the phase transition temperature (T c ≈ 39C). Lamellar domain structure with the phase contrast due to 180 domains is observed for the surfaces perpendicular to the polar direction. Local hysteresis loops acquired by SPM are well saturated with the average coercive voltage of ∼15 V. The shape of the loops is found to depend on the stiffness of the SPM cantilever. Local studies are complemented with the macroscopic measurements (polarization, piezoelectric coefficient, dielectric permittivity) performed in the temperature range including T c (20-39C). The mechanisms of the domain contrast and prospects of using MAPBB for high-density data storage are discussed.