We report a fabrication of arrays of ferromagnetic iron and cobalt nanocluster wires (NCWs), ranging from 8 to 10 nm in diameter and up to a few millimeters in length. The iron and the cobalt nanoclusters served as building blocks of the corresponding ferromagnetic NCWs. The iron and the cobalt nanoclusters were produced by thermally decomposing the corresponding metal carbonyl vapors with a resistive heater placed in the middle of a pair of permanent disk magnets. The NCWs were produced through pile-up of metallic nanoclusters along lines of magnetic flux, perpendicularly to the substrates attached to a pair of permanent disk magnet surfaces. We observed coercivities as large as 248 and 964 oersteds and remanences as high as 61 and 71% for the ferromagnetic iron and cobalt NCWs, respectively.There is no doubt that the nanowires (NWs) have drawn a special attention from all of us because of their properties quite different from the bulk, resulting from nanometer-scale onedimensional structure and their potential applicability to engineer a variety of state-of-the-art nanodevices. 1 For instance, the most spectacular of these may be arrays of ferromagnetic NWs which may be useful for a perpendicular magnetic recording. [2][3][4] In this work, we report a very easy fabrication of arrays of ferromagnetic nanocluster wires (NCWs), including characterization of their structures, physical dimensions, and magnetic properties. Here, the NCW is named because the NW consists of metallic nanoclusters.The experimental setup used in the present experiment is quite simple, as represented in Figure 1. Here, the stainless steel reaction chamber is very similar to the one used to generate a variety of metallic nanoclusters by thermally decomposing metal carbonyl vapors with a resistive heater in the previous work. 5 The reaction chamber was evacuated with a 50 L/s mechanical pump down to 10 -3 Torr. Even at this vacuum level, metallic
It is an intrinsic question whether or not the small metallic nanoclusters might have a structure different from the bulk structure. We observed a face-centered-cubic ͑fcc͒ structure for small Cr and Mo nanoclusters rather than a bulk body-centered-cubic ͑bcc͒ structure. We determined the critical cluster size n crit to be 490Ϯ100 for metallic Cr nanoclusters and the range of the n crit to be 1460-3900 for metallic Mo nanoclusters at which a structural transition from the fcc structure into the bulk bcc structure occurred.
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