Crystallographic and magnetic properties of Ti xCo 1+ xFe 2−2 xO 4 ferrite powders

Abstract

The Ti x Co 1+ x Fe 2−2 x O 4(0.0⩽ x⩽0.7) ferrite powders are fabricated by a sol–gel method. The growth of particles, crystallographic and magnetic properties of powders are investigated by X-ray diffraction, Mössbauer spectroscopy and vibrating sample magnetometer. Ti x Co 1+ x Fe 2−2 x O 4 (x=0.2) ferrite powder annealed at and above 873 K have only a single spinel structure and behave ferrimagnetically. Powder annealed at 773 K has a typical spinel structure and shows a paramagnetic and ferrimagnetic nature, simultaneously. The formation of nano-crystallized particles is confirmed when Ti x Co 1+ x Fe 2−2 x O 4 ( x=0.2) powder is annealed at 673 K. The magnetic behavior of powders annealed at and above 673 K shows that an increase in the annealing temperature yields a decrease in the coercivity and, in contrast, an increase in the saturation magnetization. In the Ti x Co 1+ x Fe 2−2 x O 4 ( x=0.2) ferrite powder the maximum coercivity and the saturation magnetization are 1564 Oe and 62.6 emu/g, respectively. All the structures of Ti x Co 1+ x Fe 2−2 x O 4 (0.0⩽ x⩽0.7) ferrite powders are spinel, and the lattice constants increase with increasing x. The Mössbauer spectra at room temperature, consisted of two Zeeman sextets (0.0⩽ x⩽0.4) due to Fe 3+ ions at tetrahedral and octahedral sites, changed gradually to a doublet ( x=0.7). The variation of Mössbauer parameters with the crystallographic and magnetic properties of powders have been discussed. The magnetic hyperfine fields decrease with increasing x in Ti x Co 1+ x Fe 2−2 x O 4(0.0⩽ x⩽0.7). The coercivity decreases fast but the saturation magnetization decreases slowly with increasing x in Ti x Co 1+ x Fe 2−2 x O 4.