Multiferroic, optical and magneto-dielectric properties with enhanced magneto-impedance characteristic of KBiFe2O5.

KBiFe 2 O 5 (KBFO) is an interesting multiferroic compound with the coexistence of ferroelectric and ferromagnetic phases with a narrow band gap. In this work, KBiFe 2 O 5 (KBFO) is synthesized using a sol-gel technique, followed by calcination at 973 K. Rietveld refinement analysis of XRD data confirms the presence of monoclinic crystal structure with space group P 2/ c. The SEM micrograph of KBFO reflects the irregular shape of grains with slight agglomeration. The optical band gap measured by UV visible spectroscopy of KBFO is found to be 1.56 eV. The multiferroic behavior of KBFO has been confirmed by the electrical (dielectric) and magnetic (M-H loop) measurements. A weak ferromagnetic nature is observed due to canting of the magnetic moment of G-type anti-ferromagnetic ordering. The dielectric studies reveal the Maxwell-Wagner type dispersion and an anomaly near magnetic phase transition temperature. KBFO shows negative magneto-dielectric (MD) coupling as both ε and tan δ decreases with the increasing magnetic field. Impedance spectroscopy is performed to analyze the intrinsic and extrinsic effects in MD coupling. The Nyquist plot shows positive magneto-resistance and negative magneto-capacitance which represent strong MD coupling in KBFO. It also reveals that the bulk property (intrinsic effect) dominates over the extrinsic effect in the sample. These results affirm that KBFO is a new candidate for room-temperature multiferroicity with a suitable bandgap and strong MD coupling for photovoltaic applications. • Crystal field splitting energy in KBFO is applied to describe the lower bandgap. • Photocatalysis effect is described using e--e- interaction influenced magnetic ordering. • The KBFO shows only a negative magneto-dielectric coupling effect. • The magneto impedance (MI) effect is considered as an interface driven effect. • KBFO shows positive magneto-resistance and negative magneto-capacitance effect. [ABSTRACT FROM AUTHOR]