International Congress on Nanoscience& Nanotechnology (ICNN2012) 8 - 10 September 2012, Kashan, I. R. Iran
The Effect of Fe addition on the Magnetic Properties of FeCoZn NW arrays M. Arefpoor1, M. Almasi Kashi1,2,*, A. Ramazani1,2, E. Golafshan1 1
Institute of Nanoscience and Nanotechnology, University of Kashan, Kashan, Iran 2 Department of Physics, University of Kashan, Kashan, Iran * E-mail:
[email protected]
Keywords: Magnetic recording media, AGFM, Magnetic nanowires, PAO templates.
Fabrication of magnetic nanowires has attracted considerable attention owing to potential applications in high density magnetic recording. Large saturation magnetization, high coercivity (Hc) and superior squarness (Sq) are essential factors for such applications. There are several techniques to fabrication of magnetic nanowires. Among them, electrodeposition in porous aluminium oxide (PAO) templates is an efficient, simple and inexpensive method. Highly ordered PAO templates were prepared by the two step anodization method as reported elsewhere [1]. A top view AFM image of PAO template is shown in figure 1. Relatively perfect hexagonally arranged nanopores with interpore distances about 100 nm can be seen. After preparing the template, FeCoZn NWs were ac pulsed electrodeposited with graphite and PAO template as counter and working electrodes, respectively. The solutions were consisted of 0.15 M CoSO4, 0.02 M ZnSO4 and two different molarities of FeSO4 : 0.15 and 0.24 M. Reduction and oxidation times were 5 ms and the off time between pulses was 100 ms. The electrodeposition voltage was 18 V p-p. Figure 2 shows a cross section view SEM micrograph of FeCoZn NWs arrays deposited into the PAO template.
Figure 1: A top view AFM image of PAO template.
Figure 2: Cross section SEM micrograph of FeCoZnNWs.
International Congress on Nanoscience& Nanotechnology (ICNN2012) 8 - 10 September 2012, Kashan, I. R. Iran The magnetic properties of NWs were measured by alternating gradient force microscopy (AGFM) at room temprature. There are several reports that FeCo NWs have Hc about 2000 to 2800 Oe [2]. Adding a nonmagnetic metal such as Zn to FeCo alloy dramatically decreases Hc of FeCoZn NWs to 600-650 Oe. Annealing these NWs at 580 C causes to Hc reaching the same amount in FeCo NWs. Melting the Zn metal during the annealing is said to segregate the FeCo magnetic grains thereby reduces the magnetostatic interaction therefore increases the Hc and Sq. The hysteresis loops are shown in figure 3 imply no significant variation in the Hc by increasing in Fe content while the Sq of the annealed FeCozn prepared in electrolyte contanining 0.15 M Fe is less than those obtained in 0.24 M Fe concentration. The increament of spontaneous magnetization is reported [3] to be responsible for such
Magnetization (arb.unit)
variations. 1.0
a
b
0.5 0.0 -0.5 -1.0 -4000
0.15 M Fe 0.24 M Fe
-2000 0 2000 Applied Field (Oe)
-4000
-2000 0 2000 Applied Field (Oe)
4000
6000
Figure 3: Hystersis loops of (a) as-deposited and (b) annealed FeCoZn NWs. In the present work a superior Hc (2720 Oe) and a high Sq (0.99) was attained which are in scope of requirement of the perpendicular high magnetic recording media [4]. References [1]M.AlmasiKashi,A.Ramazani,A.Khayyatian,“The influence of the ac electrodeposition conditions on the magnetic properties and microstructure of Co nanowire arrays”,J.Phys.D, 39(2006)4130. [2] W. Chen, S. Tang, M. Lu, Y. Du,“The magnetic properties and reversal of Fe–Conanowire arrays”, J. Phys.: Condens. Matter,15 (2003) 4623. [3] J.C. Slater, J. Appl. Phys, 8(1937)385. [4] I. Kaitsu,R. Inamura, J. Toda,T. Morita,“Ultra high density perpendicular magnetic recording technologies”, Fujitsu Sci. Tech. J., 42(1)(2006) 122.
