Magnetic properties of α-Fe2O3 nanowires
Introduction
Recently, the antiferromagnetism in nanosized systems attracts much attention. The oxides of Fe are extensively used in the fields of semiconductor, record material, light catalyst etc. Because of the novel physical and chemical properties, nano α-Fe2O3, as a popular oxide of Fe, is a focus of researches. Now nanosized α-Fe2O3 in thin films and particles has been prepared and studied systematically. A few works have been done in the synthesis and characteristics of α-Fe2O3 nanowires. Here, we report some interesting magnetic properties of the α-Fe2O3 nanowires prepared by oxygenating pure iron.
Recent researches show that antiferromagnetic α-Fe2O3 has three critical temperatures: Neel temperature, blocking temperature, and Morin temperature. Between the blocking temperature and Neel temperature (TB < TN), the intraparticle atomic moments lock together cooperatively and order antiferromagnetically under the influence of exchange interaction and the system responds reversibly or superparamagnetically to changes in applied field within the time scale of the measurement [1], [2] for the disordered individual nanoparticle moments. In DC magnetization measurements, there is always a cusp at TB.
α-Fe2O3 also goes through Morin transition at a lower temperature, TM (usually, TM < TB), above which the spins lie in one of the vertical planes of symmetry, and a weak ferromagnetism appears due to a slight angle between the spins of the two magnetic sublattices. And, at the temperatures below the Morin transition, two magnetic sublattices are oriented along the rhombohedral [1 1 1] axis and are exactly antiparallel [3], [4]. The Morin temperature was found to be strongly dependent on particle size, tending to disappear (<5 K) below a diameter of 8–20 nm [5], [6].
Section snippets
Experimental
The α-Fe2O3 nanowires were prepared by oxygenating pure iron, which has been detailed in [7], [8]. By carefully controlling the temperature, pressure, and reacting time, pure iron was heated in a flow of oxidizing atmosphere. Reaction between iron and mixed gas at 550–650 °C for several 10 h resulted in the nanowires of α-Fe2O3 on the surface of iron substrate. The diameters of most of the nanowires range from 10 to 20 nm, and their typical length is in the range of 10–20 μm. Analytical
Results and discussion
Fig. 1 shows the temperature dependence of the zero-field-cooled (ZFC) and field-cooled (FC) magnetization from 4 to 200 K under an applied field of 100 Oe. From the M–T curve, it shows TB ≈ 120 K and no significant evidence of Morin transition. Above 120 K, the FC and ZFC magnetization curves exhibit the same trend and overlap. Below TB (120 K), the curves split significantly. The ZFC magnetization decreases sharply, while the FC magnetization rises significantly. From 4 to 100 K, both ZFC and FC
Acknowledgment
The project was financially supported by NSFC under Grant No. 10374003.
References (13)
- et al.
Chem. Phys. Lett.
(2001) - et al.
Chem. Phys. Lett.
(2003) - et al.
J. Magn. Magn. Mater.
(2001) - et al.
J. Magn. Magn. Mater.
(2001) Ann. Geophys.
(1949)Phys. Rev.
(1963)
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