Ferromagnetic properties of conducting filament nanodots formed on epitaxial BiFeO3 thin film

Abstract

We investigate the ferromagnetic properties of the conducting filament (CF) nanodots formed on epitaxial BiFeO3 (BFO) thin film, which exhibit resistive switching behavior. 50-nm thick epitaxial BFO thin film was grown on Nb-doped SrTiO3 single crystal substrates through pulsed laser deposition. The ferroelectric microcapacitor fabricated using the epitaxial BFO thin film shows excellent ferroelectric properties with a remanent polarization of approximately 32 μC/cm2 and unipolar resistive switching behavior. CF nanodots with a diameter of approximately 16 nm are formed in the local region of the BFO thin film through conductive atomic force microscopy. Generally, ferromagnetic materials exhibit superparamagnetism, on a scale of tens of nanometers, as a result of the thermal energy of the magnetic moments. In this study, magnetic force microscopy demonstrates that the CF nanodot possesses ferromagnetism. It is suggested that exchange coupling between the CF nanodot and surrounding BFO causes the ferromagnetism of the nanodot. Our study provides new insight on the design of multistate memory cells with resistive switching and magnetic spin ordering, for application in high-density information storage media.