Evidence of room-temperature magnetodielectric effect in brownmillerite KBiFe 2 O 5 through magnetic, complex dielectric
- PDF / 4,629,614 Bytes
- 10 Pages / 595.276 x 790.866 pts Page_size
- 63 Downloads / 194 Views
Evidence of room‑temperature magnetodielectric effect in brownmillerite KBiFe2O5 through magnetic, complex dielectric, and impedance study K. Chandrakanta1 · R. Jena1 · P. Pal1 · Md. F. Abdullah1 · S. R. Mohapatra3 · S. D. Kaushik2 · A. K. Singh1 Received: 18 June 2020 / Accepted: 31 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract We have investigated the structural, magnetic, dielectric, and magnetodielectric properties of brownmillerite-structured polycrystalline KBiFe2O5 (KBFO) sample synthesized using conventional solid-state reaction route. Monoclinic structure with P2/c space group is determined from Rietveld refined X-ray diffraction (XRD) analysis. Temperatures-dependent magnetic and dielectric data show a broad hump around 510 °C, indicating the existence of magnetodielectric effect in KBFO. Room-temperature M–H hysteresis measurement possesses a weak ferromagnetic order (MR = 0.006 emu/g and Hc = 1100 Oe) originating from the canted Fe3+ moments due to antiferromagnetic ordering. This canted Fe3+ moment is also reflected in magnetic field variation of magnetodielectric (MD) measurement at room temperature, in which MD does not trace the original path by reversing the field. The highest magnetodielectric response is obtained to be ~ − 1.8% at room temperature. Modulus and complex impedance spectrum analysis attributes the bulk contribution to the observed room-temperature magnetodielectric at high frequency (> 10 kHz) and extrinsic contribution ( 2 kHz). Here two different values of ‘n’ signify two different kind of contributions to MD effect at room temperature in KBFO. At an applied field of 0.2 T, the extracted exponents from the fitting of MD% data are n ~ − 0.5 (for f ˂ 2 kHz) and n ~ − 0.1 (for f ˃ 2 kHz). Similar kind of behavior is observed for all the MD data at the applied field of 1 T and 1.2 T. The appearance of frequency-dependent MD peak at higher frequency for all the values of applied magnetic field suggests either change of dipolar relaxation dynamics with the external magnetic field. As the peak position of MD% data with frequency at different applied magnetic field remains unaltered, it rules out the existence of fieldinduced dipolar relaxation process. This type of behavior of MD% versus frequency data suggests the intrinsic origin of magnetodielectric effect at high frequency [25]. At low frequency, the linear increase in MD% up to a particular frequency suggests the extrinsic origin. Maxwell–Wagner polarization, material–electrode interface can also give rise to MD effect that are of the extrinsic
13
Fig. 5 a Room-temperature frequency variation of magnetodielectric (MD) % of KBFO sample under different selected magnetic field strength. Inset shows the power law fitting of the form MD α exp(ω)n. b Room-temperature field variation MD% of KBFO sample at 30 kHz
origin [19]. To understand the above field-dependent and relaxation mechanism in MD behavior, field variation of MD% and impedance analysis is carried out. The magnetic field de
Data Loading...
