Magnetic, dielectric and microwave properties of M-Ti substituted barium hexaferrites (M=Mn2+, Co2+, Cu2+, Ni2+, Zn2+)

Abstract

Several divalent cations together with tetravalent Ti4+ ion were replaced by two trivalent Fe3+ ions of barium hexaferrite in the form of BaFe10M2+Ti4+O19. Samples were prepared by using solid state reaction route and 1 wt% B2O3 was added to inhibit the crystal growth at lower temperatures. Magnetic, dielectric and microwave properties of samples were investigated by X-ray crystallography, scanning electron microscopy, magnetization and near field microwave measurements. Magnetization measurements revealed that saturation magnetization of the cation substituted samples is less than that of the pure barium hexaferrite. Except Co2+ substituted barium hexaferrite, coercivities of the samples are nearly 1 kOe. While measurement of dielectric constants of Zn2+, Mn2+, Co2+ and Cu2+ substituted samples yields a significant enhancement ( approximate to 10-10(2) times) with respect to Ni2+ substituted barium hexaferrite in permittivity through local polarization of Fe3+ electronic charges activated with nearby divalent ions. It is suggested that Zn2+ and Mn2+ substitution acts to reduce the electron hopping probability between Fe2+ and Fe3+. All samples have approximately the same microwave absorption properties in such a way that minimum reflection loss (RL) of -10 dB occurs at 15 GHz. Meanwhile, Zn2+ and Mn2+ substituted samples have quite wide absorption bandwidths of 4 GHz at - 10 dB. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.