Enhancement of low-field magnetoresistance in Fe3O4 particles induced by ball milling

A series of Fe3O4 particles with different size have been obtained by mechanical ball milling from t=0–450 h. Crystal structure and microstructure of the samples are analyzed by XRD and SEM. An emphasis has been placed on magnetic and transport properties. The experimental results indicate that the sample t=350 exhibits an enhancement of magnetoresistance (MR) comparing with initial powder compress sample (t=0). The low-field magnetoresistance reaches MR=−6.04% at Verwey temperature 120 K and MR=−2.54% at 290 K. Thermal behavior TGA analysis and investigation of magnetic properties have revealed that there is an oxide layer on surface of Fe3O4 particles. It is considered that the enhanced magnetoresistance can be taken into account in terms of spin-dependent tunneling effect between Fe3O4 particles.Temperature dependence of magnetization and resistivity are measured in order to study electrical and magnetic behavior near Verwey transition. In addition, we also discuss ball milling time dependence of coercivity Hc and specific magnetization Ms of these samples.