On the inter-layer magneto-electric coupling in BiFeO₃/SrRuO₃ heterostructure

Abstract

Interlayer magneto-electric coupling in BiFeO₃/SrRuO₃ heterostructures was investigated by impedance spectroscopy over a temperature range of 80 K–260 K. In-plane impedance measurements were performed using interdigitated gold electrodes fabricated on the BiFeO3 layer. The Nyquist plots at different temperatures were fitted with an equivalent circuit model of the heterostructure. A pronounced dip in the temperature coefficient of equivalent-capacitance and a distinct increase in the temperature coefficient of equivalent-resistance of the BiFeO₃ layer were observed on cooling across ferromagnetic TC of the bottom SrRuO₃ layer. Temperature dependent capacitance (at 0 T magnetic fields) and magneto-capacitance (at 5 T magnetic fields) plots showed anomalies near 160 K. A shift of the hysteresis loop along the magnetization axis in field cooled M-H measurements was also found, which indicates the presence of pinned SrRuO₃ moments due to the magnetic interaction at the interface. These observations suggest a strong magneto-electric coupling between the BiFeO₃ and SrRuO₃ layers of this heterostructure.