Study of Magnetic Properties and Relaxation Time of Nanoparticle Fe3 O4-SiO2

Abstract

The magnetic properties and relaxation time of Fe3 O4 nanoparticles, and their encapsulation with silicon dioxide (Fe3 O4-SiO2 ), have been successfully investigated by analyzing the temperature dependence of magnetization (M(T)) and the time dependence of magnetization (M(t)), using the SQUID magnetometer measurement. The M(T) measurement results can determine the magnetic parameters and magnetic irreversibility of Fe3 O4 and Fe3 O4-SiO2 samples. The values of Curie constant (C), effective magnetic moment (µe f f ), and Weiss temperature (θP ) are 4.2 (emu.K.Oe/mol), 5.77 µB, and −349 K, respectively, for the Fe3 O4 samples, and 81.3 (emu.K.Oe/mol), 25.49 µB, and −2440 K, respectively, for the Fe3 O4-SiO2 samples. After encapsulation, the broadening peak deviation decreased from 281.6 K to 279 K, indicating that the superparamagnetic interactions increased with the encapsulation process. The magnetic parameters and irreversibility values showed that the superparamagnetic properties increased significantly after encapsulation (Fe3 O4-SiO2 ). From the results of the M(t) measurement, it was found that there was a decrease in the magnetic relaxation time after the encapsulation process, which indicated that the distribution of the nanoparticle size and anisotropy energy increased.