Structural, dielectric and magnetic properties of Cr–Zn doped strontium hexa-ferrites for high frequency applications

Abstract

M-type strontium hexa-ferrite nano particles with composition SrFe12−2xCrxZnxO19 (X=0.0, 0.2, 0.4, 0.6, 0.8) were prepared by co-precipitation method and are reported for the first time. X-ray diffraction analysis confirmed the successful substitution of Cr and Zn ions in the strontium hexa-ferrite lattice. Structural morphology studied by scanning electron micrographs revealed that Cr–Zn doping inhabits the grain growth. Dielectric measurements were taken as a function of frequency in the range (10kHz to 3MHz). Both dielectric constants and dielectric losses were found to be decreasing with the increase in Cr–Zn concentration. As Cr–Zn doping favored the decrease in dielectric losses to a large extent (0.32–0.02) so the strontium hexa-ferrite with these dopants is very useful for high frequency applications. The frequency dependent ac conductivity increases sharply at higher frequencies due to increase in hopping frequency of electrons and decrease with the increase in doping concentration and this is due to decrease in Fe2+ ions. Temperature dependent dc electrical resistivity measurements showed a decreasing trend with the increase in Cr–Zn concentration. The M–H loop indicated that both coercivity and saturation magnetization were decreased with the increase in doping concentration. The former was decreased due to increase in grain size and later was decreased due to weak and non-magnetic cations distribution on interstitial sites.