Fabrication of Dispersed Permalloy Nanoparticles by Pulsed Laser Ablation in Aqua
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Fabrication of Dispersed Permalloy Nanoparticles by Pulsed Laser Ablation in Aqua Ruqiang Bao1, Zijie Yan1, Yong Huang2 and Douglas B. Chrisey1 1 Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA 2 Department of Mechanical Engineering, Clemson University, Clemson, SC 29634, USA ABSTRACT Permalloy (Ni81Fe19) nanoparticles with diameters of hundreds of nanometers have been successfully fabricated by pulsed laser ablation (PLA) in air, distilled water, pure ethanol and sodium dodecyl sulfate (SDS) aqueous solutions. The permalloy nanoparticles made in SDS solutions are typically spherical in shape. Lower laser energy with lower frequency leads to the formation of smaller permalloy nanoparticles. Higher concentration of SDS results in smaller nanoparticles. Lastly, we found some unusual permalloy nanoparticles with interesting morphologies made by PLA in air, distilled water and ethanol. INTRODUCTION Permalloy is a magnetic alloy known for its high bulk magnetic permeability, low coercivity, significant anisotropic magnetoresistance and near zero magnetostriction, which are critical for commercial applications such as recording heads. Many of characteristic magnetic properties of permalloy are known to depend on the size and microstructure of the particles [1]. Therefore, it would be interesting to reduce the size of magnetic grains of permalloy to explore changes in the magnetization. Many efforts have been made to prepare permalloy thin films and nanodots aiming to study the magnetic properties of these low-dimensional permalloy structures [2]. Nano-dots are usually fabricated by electron-beam lithography and a lift off process, thus they should be fabricated on substrates which permit the application of them. Practical applications may require free standing and reproducible permalloy nanostructures. Recently, Cushing et al. [3] tried to synthesize permalloy nanoparticles by water-in-oil micro-emulsions with NiCl2·6H2O, FeSO4·7H2O, NaBH4 and HAuCl4 as reactants. However, the purity and composition of the prepared particles is questionable. Pulsed laser ablation (PLA) became popular in the late 1980s due to its high potential in complex materials processing such as thin film deposition, nanocrystal growth, and microelectronic device fabrication [ 4 ]. The advantage of its amenability to conventionally harsh processing conditions means it could be done in corrosive gas environments, in atmospheric environments, and even in the liquid [5]. Many researchers have employed PLA to prepare nanostructured materials, including diamond nanoparticles [6], noble metal nanocrystals [7,8], such as ultrafine Au, Ag and Pt particles, and alloys [9] and oxide nanostructures [10] in various liquid environments, including water, methanol, isopropanol, and SDS aqueous solution. For example, the ultra-fine Au, Ag and Pt nanoparticles (less than 5 nm in diameter) were fabricated by PLA (532 nm) of metal targets in SDS aqueous solution [11]. Although permalloy nanoparticles ha
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