Magnetic properties of the granular alloy Fe10Ag90 as a function of annealing temperature

AUTOR(ES)

Soares, João Maria, Araújo, José Humberto de, Cabral, Francisco de Assis Olímpio, Dumelow, Thomas, Xavier Júnior, Milton Morais, Sasaki, José Marcos

FONTE

Materials Research

DATA DE PUBLICAÇÃO

2005-09

RESUMO

Fe10Ag90 granular alloys have been prepared using a sol-gel process, sintered at 300 °C and annealed at temperatures between 400 °C and 700 °C. The mean size of the iron particles, obtained from X-ray diffraction, is 30.0 ± 0.7 nm. Due to the existence of a distribution of particle sizes in these samples, both blocked (BL) and superparamagnetic (SPM) particles are present simultaneously, as confirmed by magnetization measurements at room temperature. AC susceptibility measurements as a function of temperature reveal a magnetic phase transition at about 770 °C, indicating the presence of particles exhibiting bulk behavior, in the samples annealed above 550 °C. The presence of these particles has been attributed to an atomic diffusion process between the grains, forming bulk-like multiple-domain Fe particles having Curie temperatures near that of bulk alpha-Fe phase (T C = 770 °C).

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