The Use of Mesoporous Systems for Preparation of One-Dimensional Ordered Magnetic Nanowires
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The Use of Mesoporous Systems for Preparation of One-Dimensional Ordered Magnetic Nanowires Andrei A. Eliseev, Kirill S. Napolskii, Dmitry F. Gorozhankin, Alexei V. Lukashin, Yuri D. Tretyakov, Dept. of Materials Science, Moscow State University, Moscow, 119992, Russia. Natalia A. Grigorieva, St-Petersburg State University, St-Petersburg, 198504, Russia. Sergei V. Grigoriev, Petersburg Nuclear Physics Institute, Gatchina, St.Petersburg, 188300, Russia. A.A. Vorobiev, Institute Laue-Langevin, B.P. 156, Grenoble Cedex 9, 38042, France. Peter Görnert, INNOVENT e.V., Prüssingstrasse 27 B, D- 07745 Jena, Germany. Fax +7-(095)-939-0998, e-mail: [email protected] ABSTRACT Here we report the synthesis and investigation of iron and iron oxide nanowire arrays using mesoporous silica as a host material. In the present work a novel variant of synthesis of ordered magnetic nanowires in the mesoporous silica matrix was suggested. The method is based on the incorporation of a hydrophobic metal compound into the hydrophobic part of silica-surfactant composite. The amount of iron intercalated into the mesoporous matrix was measured by chemical analysis. In all samples it corresponds well to with the molar ratio SiO2 : Fe = 9:1. To provide crystallinity of nanowires additional thermal treatment was performed. Thus prepared nanocomposites were characterized by TEM, ED, SAXS, SANS, BET and magnetic measurements. The anisotropy parameters of nanowires were determined using two noncorrelated methods: temperature dependence of magnetic susceptibility and small angle polarized neutron scattering. It was found that the particle length increases with the increasing of the decomposition temperature of the metal complex. Obviously it deals with crystallization and growth of metal particles inside the pores at a constant diameter of a single particle. For iron containing sample annealed at 375 оC (form factor of nanowire is about 40), the coercive force at room temperature was found to be 145 Oe at saturation magnetization of 1.2 emu/g, which is not far from modern information storage. It was shown that particles shape and size are in good agreement with that of the pores. Particles are uniform and well ordered in the silica matrix. Thus, the suggested method leads to one-dimensional anisotropic nanostructures which could find an application as high-density data storage magnetic media. 1. INTRODUCTION An exceptional growth of information technologies resulted in the necessity for storage and handling a colossal volume of digital information. The main branch of industry of the information carriers today relies upon magnetic information storage. Recently several techniques such as Perpendicular Recording, Heat Assisted Magnetic Recording, Antiferromagnetic Coupling were suggested to increase the areal density, time-temperature stability and signal-tonoise ratio in magnetic storage devices [1]. The further improvement of the density requires the development of principally new magnetic materials with high saturation magnetic flux de
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