Room temperature ferromagnetic behavior in Cr2O3 nanoparticles prepared by a planetary ball mill system

Abstract

Abstract Recently, room temperature ferromagnetism (RTFM) has been reported to be found in many kinds of oxide semiconductor nanoparticles. The origin of the magnetic moment is believed to be defects because RTFM strongly depends on particle size. In this study, we have focused on the antiferromagnetic insulator Cr2O3 due to the interesting core-sell structure (RTFM/antiferromagnetism). Furthermore, RTFM found in oxide nanoparticles is expected to depend on the sample preparation condition. Here, the effect of sample preparation condition on RTFM was investigated. Samples were nanoparticles prepared by milling oxide powders in Ar or air circumstances. Both samples indicated hysteresis at room temperature. At higher temperatures than the Néel temperature (308 K), hysteresis loops were found. A significant difference was observed in the saturation magnetization. The sample prepared in air has four times smaller saturation magnetization in 60 min milling time due to self-compensation of defects with air.