Magnetic transitions in α-Fe2O3 nanowires

Abstract

Magnetic transitions in single-crystal α-Fe2O3 (hematite) nanowires, grown by thermal oxidation of iron powder, have been studied in the range of 5–1023K with a superconducting quantum interference device below room temperature and with a vibrating sample magnetometer at higher temperatures. The broad temperature range covered enables us to compare magnetic transitions in the nanowires with the transitions reported for bulk hematite. Morin temperatures (TM) of the nanowires and of hematite bulk reference powder were found to be 123 and 263K, respectively. Also the Néel temperature (TN) of the nanowires, 852K, was lower than the bulk TN value. Measurements of the magnetization as a function of temperature show an enhanced signal in the nanowires, which suggests a decrease in the antiferromagnetic coupling. A coercive field observed below TM in the hysteresis loops of the nanowires is tentatively explained by the presence of a magnetic phase.