Artículos de revistas
Structure and magnetic properties of granular NiZn-ferrite - SiO2
Registro en:
Materials Research. ABM, ABC, ABPol, v. 2, n. 3, p. 235-238, 1999.
1516-1439
S1516-14391999000300021
10.1590/S1516-14391999000300021
Autor
Albuquerque, Adriana Silva de
Ardisson, José Domingos
Bittencourt, Edison
Macedo, Waldemar Augusto de Almeida
Institución
Resumen
Granular systems composed by nanostructured magnetic materials embedded in a non-magnetic matrix present unique physical properties that depend crucially on their nanostructure. In this work, we have studied the structural and magnetic properties of NiZn-ferrite nanoparticles embedded in SiO2, a granular system synthesized by sol-gel processing. Samples with ferrite volumetric fraction x ranging from 6% to 78% were prepared, and characterized by X-ray diffraction, Mössbauer spectroscopy and vibrating sample magnetometry. Our results show the formation of pure stoichiometric NiZn-ferrite in the SiO2 matrix for x < 34%. Above these fraction, our samples presented also small amounts of Fe2O3. Mössbauer spectroscopy revealed the superparamagnetic behaviour of the ferrimagnetic NiZn-ferrite nanoparticles. The combination of different ferrite concentration and heat treatments allowed the obtaintion of samples with saturation magnetization between 1.3 and 68 emu/g and coercivity ranging from 0 to 123 Oe, value which is two orders of magnitude higher than the coercivity of bulk NiZn-ferrite. 235 238 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)