In situ observation of electric-field induced magnetic domain evolution in (Ba,Ca)(Ti,Zr)O${}_3$-CoFe${}_2$O${}_4$ multiferroic films

The integration of ferroelectric and ferromagnetic promises an essential strategy of obtaining high performance electronic devices. In this work, we demonstrate in situ observation of electric field induced magnetic domain structure evolution for 0.5Ba(Ti${}_{0.8}$Zr${}_{0.2}$)O${}_3$-0.5(Ba${}_{0.7}$Ca${}_{0.3}$)TiO${}_3$-CoFe${}_2$O${}_4$ (BZT-0.5BCT/CFO) films, which manifests the magnetoelectric (ME) coupling between ferroelectric BZT-0.5BCT and ferrimagnetic CFO. The multiferroic behaviors of BZT-0.5BCT/CFO bilayers thin films were characterized by measuring ferroelectric domains, ferroelectric and ferrimagnetic hysteresis loops. The magnetic domain structure were investigated as functions of electric field, when the sample is applied with a voltage of 3 V, approximately 49.2% of the magnetization domain was varied in CFO thin films. The modulation of the domain structure could be attributed to the strain-induced mechanical transduction between the ferroelectric and magnetic films and modulation of the electron density of the CFO films. Direct observation of electric field induced magnetic domain evolution is significant since it gives a direct evidence of magnetoelectric coupling effect.