Magnetic Field‐Induced Ferroelectric Switching in Multiferroic Aurivillius Phase Thin Films at Room Temperature

Abstract

Single‐phase multiferroic materials are of considerable interest for future memory and sensing applications. Thin films of Aurivillius phase Bi 7 Ti 3 Fe 3 O 21 and Bi 6 Ti 2.8 Fe 1.52 Mn 0.68 O 18 (possessing six and five perovskite units per half‐cell, respectively) have been prepared by chemical solution deposition on c ‐plane sapphire. Superconducting quantum interference device magnetometry reveal Bi 7 Ti 3 Fe 3 O 21 to be antiferromagnetic ( T N = 190 K) and weakly ferromagnetic below 35 K, however, Bi 6 Ti 2.8 Fe 1.52 Mn 0.68 O 18 gives a distinct room‐temperature in‐plane ferromagnetic signature ( M s = 0.74 emu/g, μ 0 H c =7 mT). Microstructural analysis, coupled with the use of a statistical analysis of the data, allows us to conclude that ferromagnetism does not originate from second phase inclusions, with a confidence level of 99.5%. Piezoresponse force microscopy ( PFM ) demonstrates room‐temperature ferroelectricity in both films, whereas PFM observations on Bi 6 Ti 2.8 Fe 1.52 Mn 0.68 O 18 show Aurivillius grains undergo ferroelectric domain polarization switching induced by an applied magnetic field. Here, we show for the first time that Bi 6 Ti 2.8 Fe 1.52 Mn 0.68 O 18 thin films are both ferroelectric and ferromagnetic and, demonstrate magnetic field‐induced switching of ferroelectric polarization in individual Aurivillius phase grains at room temperature.