Magnetic Interactions Study in ZnO Doped with Fe Ions Produced by Thermal Diffusion Processes
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Magnetic Interactions Study in ZnO Doped with Fe Ions Produced by Thermal Diffusion Processes R. Baca1, M. Galván3, J. V. Méndez2, J. A. Andraca2 and R. Peña3 1 Department of Electronics, National Polytechnic Institute, 07738, México City, México. 2 Department of Nanoscience and Microtechnology, National Polytechnic Institute, 07738, México City, México. 3 Department of Electrical Engineering, CINVESTAV, 07360, México City, México. ABSTRACT Recently, the oxides have received attention and great interest due to their magnetic ordering above of the room temperature by doping a very low amount of transition metal ions, which are very promising for applications such as biosensing, hyperthermia, doped magnetic semiconductors with lower energy losses and rapid response at alternating-magnetic fields. In this work the magnetic interactions on Fe doped ZnO thin-films was studied. Raman spectroscopy allowed the monitoring of iron ions diffusion and demonstrated that symmetry modes are crucial for understanding of the magnetic ordering. X-ray diffraction (XRD) was used to determine the oxidation state of the iron ions and stress into ZnO lattice. MFM confirmed that magnetic moments and magnetic forces on scanned surface depend on magnetic-domain structure formation. INTRODUCTION Spin-based multifunctional devices using electron spin in addition to charge may lead to semiconductor with greatly increased functionality being optically transparent, and having electrical and magnetic control by defect concentration [1, 2, 3], which would lead to devices such as biosensors with Fe doped ZnO thin-films and sensitive to glucose concentration, because Fe3+ ions introduces redox centre in ZnO [4]. Magnetic nanoparticles (MNP) can be made to generate local heat in vivo, which lead to their use as hyperthermia agents to destroy the tumor cells [5]. In this work we study the magnetic interactions in ZnO thin-films doped with Fe ions motivated on previous challenges. THERMAL DIFFUSION PROCESSES It is known that under air atmosphere ZnO can be formed, and Zn ions going into a sequence of jumps between occupied interstitial sites [6, 7], and Į-Fe2O3 (hematite phase) can be obtained, when iron foils from 200 o C are heated in humidity atmosphere [8]. Fe doped ZnO thin-films were deposited on quartz substrates by thermal diffusion processes in air atmosphere into two stages. In first stage, alternative layers of grain-oriented silicon-iron foils and zinc granules (4N purity) were deposited sequentially by vacuum evaporation. As a second stage, the deposited layers were heated in air atmosphere at 420 o C, 520 o C, and 620 o C with duration of 10min into resistively heated quartz tube furnace.
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Figure 1. Schematic model of interstitial Fe3+ movement into ZnO layer. The thickness of both films was 300nm and was measured by a Tencor profilometer. At high temperature (> 420 o C), small amounts of iron ions into ZnO occurs randomly, because the diffusion coefficient DFe of interstitial Fe3+ ions increases as a function of its activation energy
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