Temperature and magnetic field controlled dielectric relaxation and magnetodielectric response in KBiFe1.9Co0.1O5 polycrystalline

Abstract

Abstract Cobalt (Co) substituted brownmillerite KBiFe2O5 (KBiFe1.9Co0.1O5: KBFCO) is synthesized by conventional solid-state reaction route. Rietveld refinement of X-ray diffraction data confirms the pure phase of KBFCO and crystallizes in monoclinic structure with P2/c space group. Surface morphology reveals that the grains are randomly distributed, and the average grain size varies in the range of 1–4 μm. The energy dispersive X-ray spectroscopy confirms that the chemical constituents of KBFCO are very close to the molar (1:1:2) ratio. The temperature (10–300 K) and frequency (500 Hz–1 MHz) dependent dielectric permittivity value decreases approximately 50% in the presence of the magnetic field (1.3 T). It confirms the signature of the magnetodielectric (MD) effect in the KBFCO sample. The magnetic field (±1.3 T) variation MD loop resembles the inverse-butterfly type behavior for the system. Both MD hysteresis and strength decrease with a decrease in temperature. A noticeable suppression in the dielectric relaxation is obtained by applying a 1.3 T magnetic field in the temperature range of 250 K–300 K. The measured MD effect is observed at a high frequency (30 kHz), suggesting the intrinsic effect is dominated in the probing temperature range. Observation of similar trends in magnetic field-dependent MD and magnetic loss (ML) loop rules out the existence of magnetoresistance origin MD effect. These results confirm that KBFCO has an excellent MD response even for a small applied field and holds great interest for future device applications.