Nanoscale Res Lett (2010) 5:1289–1294 Fig. 1 a planar view SEM image of ZnFe2O4 nanowires within AAO templates and corresponding EDS result is shown in the inset b TEM image c HRTEM image and d SAED pattern of ZnFe2O4 nanowires 1291 Fig. 2b can be indexed as (220), (311), and (440) of spinel- type lattice structure, and the [220] texture is along the axis of the ZnFe2O4 nanowire arrays. XRD pattern of the ZnFe2O4 powders is shown in the inset of Fig. 1b for comparison. The schematic of the possible formation process of preferred oriented ZnFe2O4 nanowire arrays is shown in Fig. 2c. The process could be described as: ZnFe2 ? 2O2 ? ZnFe2O4. The XRD result shows that the ZnFe2 alloy nanowires have the preferred [110] crystal orientation along the axis of nanowires, which combined with the minor holes of AAO templates playing an important role to make the growth of ZnFe2O4 nanowire arrays largely guide along the nanowire axis direction when heat treated. To sum up, there are two main conditions that make the nanowire arrays prefer crystal orientation: the one is the well orientation of original metal crystal, and the other is the spatial conﬁnement of the minor hole. The magnetic hysteresis loops recorded at 300 and 80 K using SQUID for ZnFe2O4 nanowire arrays within AAO templates are shown in Fig. 3, where // and \ represent that the applied ﬁeld H is parallel and perpendicular to the major nanowire axis, respectively. The slope of the linier contribution in the saturation region has been subtracted. It can be seen that the magnetic hysteresis loops in parallel and perpendicular directions at both 300 and 80 K are separating, indicating the existence of magnetic anisotropy for preferred oriented ZnFe2O4 nanowire arrays, and magnetic easy axis is directed along the wire axis. Nearly, zero coercive forces are observed at 300 K both in the parallel and in the perpendicular direction (Hc// = 5 Oe and Hc\ = 3 Oe). The magnetic hysteresis loops measured at 80 K indicate the coercivity (Hc) and squareness ratio (M/Ms) are about 290 Oe (Hc//), 125 Oe (Hc\), 0.21 (M/Ms//), and 0.08 (M/Ms\), respectively, where the mag- niﬁed view of the magnetic hysteresis loops is shown in right bottom insets in Fig. 3a and b, respectively. The magnetic hysteresis loops of ZnFe2 nanowire arrays within AAO templates recorded at RT by VSM are shown in left top inset of Fig. 3a for compared. As we known, bulk Zn-ferrite belongs to the normal spinel structure with paramagnetic properties at RT and long range antiferromagnetic order below 10 K [35]. However, nanocrystalline zinc ferrite is of great interest due to its unique magnetic properties that differ substan- tially from its bulk counterpart [10]. The occupancy of Fe3? ions on both A- and B-sites leads to strong negative superexchange interaction between Fe3? ions with large 123