Pressure-tuning ferroelectric relaxation process in BaFe₄O₇

Low-energy ferroelectric photocurrent switches hold promise for optoelectronic devices and digital logic gates. Pressure, a clean and efficient method for microstructure tuning, can significantly affect the polarization photocurrent relaxation process. Upon negative poling, the photocurrent switching in a narrow bandgap ferroelectric BaFe₄O₇ single crystal from a negative direction to a positive direction during polarization photocurrent relaxation was observed under pressure. Notably, this photocurrent switching time (τ) is boosted up by more than ten folds, from 0.2 to 5 GPa, followed by a slow reduction to around 20 GPa. The very low pressure (0.2 GPa) that induces the PPR process and the τ tuned by slight lattice distortions highlight the feasibility of environmental pressure control of PPR in ferroelectric materials for practical applications. This pressure-induced behavior arises from the coupled effect of the ferroelectric remanent field and micro-ferroelectric domain relaxation process after the external poling electric field is removed. The broad range of switching times under pressure allows one to precisely control the photoelectric switch applications.