Study of Dielectric and Magnetodielectric Properties of Y-Type Ba2Mg1.5Ni0.5Fe12O22 Hexaferrite

Abstract

Hexaferrite materials continue to be interesting due to their remarkable electrical, magnetic, ME properties, and potential applications in electronic devices [1]. Recently, Y-type hexaferrite has attracted attention for their possibility of tailoring electrical, magnetic and magnetoelectric (ME) properties by varying doping and sintering condition. We have investigated dielectric and magnetodielectric (MD) properties of polycrystalline Y-type hexaferrite Ba2Mg1.5Ni0.5Fe12O22 (BMNF). Rietveld refinement of the X-ray diffraction pattern and hexagonal plate-like Field Emission Scanning Electron Microscope (FESEM) micrograph confirms the phase purity with rhombohedral crystal structure (R-3m space group). The dielectric permittivity plot of BMNF can be subdivided into three temperature regions: low-temperature region I (below 150°C), intermediate temperature region II (150°C to 290°C), and high-temperature region III (above 290°C). In the low-temperature region, slight dispersion in ε׳ with temperature is noticed. A plateau-like temperature independent dielectric permittivity is observed in the intermediate temperature. Above 290°C, the dispersion of (ε׳ (increases with increase in temperature. Fitting of Nyquist plots (Z″ versus Z´) of BMNF sample measured in the temperature range 100°C≤T≤280°C by considering bricks layer model shows the non-Debye type heavier [2]. The DC conductivity of grain (σg) and grain boundary (σgb) with respect to inverse of temperature in the Arrhenius plots manifested that σg is always greater than the σgb except an anomalous behaviour around 290 °C. The difference between σg and σgb is due to pilling of charge carrier near to the grain boundary that producing polarization. The comparable value of activation energy extracted from impedance spectroscopy above 290°C between σg and σgb shows that relaxation and conduction mechanism may be attributed to the same entities. Room temperature magnetodielectric (MD) at 1MHz indicates the step-like linear increase with the applied field but in magneto loss (ML) it is step-like linear decrease. The step-like behavior both in MD and ML may be due to the evolution of different intermediate electrical polarization with the applied magnetic field. In order to further investigate the origin of magnetodielectric effect is either due to intrinsic (spin ordering) or extrinsic (Maxwell–Wagner effect),[3] we have proposed to do pyroelectric current and magnetoresistant measurement.