2017 Progress In Electromagnetics Research Symposium — Fall (PIERS — FALL), Singapore, 19–22 November Magnetic Properties of Nanoparticles Prepared from α-Fe Target by Laser Ablation in Liquids M. M. Nosan 1, 2 , A. S. Omelyanchik 1, 2 , I. G. Samusev 1, 2 , N. M. Myslitskaya 1, 3 , R. Y. Borkunov 1 , I. I. Lyatun 1 , V. V. Rodionova 1, 2 , and V. V. Bryukhanov 1, 2 1 Immanuel Kant Baltic Federal University, Kaliningrad, Russia 2 Center for Functionalized Magnetic Materials (FunMagMa) Immanuel Kant Baltic Federal University, Kaliningrad, Russia 3 Kaliningrad State Technical University, Kaliningrad, Russia Abstract— This study aims to examine nanoparticles fabrication by nanosecond and femtosec- ond laser ablation of iron target in different liquids. Effect of liquid environment, pulse width and power of beam on the magnetic properties of produced nanoparticles have been studied experi- mentally by measuring the hysteresis loops at room temperature. It was found that saturation magnetization was increased by an order of magnitude for samples prepared by femtosecond laser. Significant change in coercive force and magnetization for samples prepared with different power of femtosecond laser beam were observed. 1. INTRODUCTION Nowadays magnetic nanoparticles have applications in many different areas such as storage sys- tem [1, 2], catalysis [3, 4], biomedicine [5, 6] etc.. There are many methods to synthesize nanopar- ticles such as co-precipitation, thermal decomposition, solvothermal routs, chemical vapor deposi- tion, arc discharge etc. and all of them fit different applications. One of the nanoparticles synthesis methods is laser ablation. Laser ablation is a complex physical and chemical process — a removal (ablation) of the substance from the surface or volume of the solid target using a laser beam. In contrast to the chemical ways of synthesis, ablative nanoparticles consist only from the material of target and the liquid (without impurities). Unlike the laser ablation in a vacuum or in a gas, laser ablation in liquid (LAL) seems to be much easier method to collect nanoparticles because they remain in the colloid form instead of being absorbed on the substrate or chamber walls [7]. In LAL, there are different factors, which can affect the result: laser type, liquid environment and laser beam power. All of them influence on ablation process differently and that is why their contributions in changing size/shape/chemical composition of nanoparticles (which lead to change in samples magnetic characteristics) are different, too [8]. The main processes of LAL are the generation, transformation and condensation of a plasma plume. However, in different modes some nuances can affect size of synthesized samples. In nanosecond (ns) and femtosecond (fs) regimes, an expansion of plasma goes different: faster in per- pendicular direction in fs laser and at similar velocity in both directions for ns laser [9]. Compared with the ns plasma, the density and temperature of the fs-derived plasma are lower and decrease faster. Furthermore, in fs regime, the phase explosion can be observed which occurs in a time scale 1 0-12 –1 0-10 s and can lead to formation of diffusion clusters [10, 11]. Environment takes part in nanoparticles formation during LAL also, and chemical reactions in LAL are different compared to ablation in gas or vacuum. Moreover, liquid can change ther- modynamic parameters by increasing pressure while plasma plume is forming. In addition, the quenching time of the laser-induced plasma in a liquid is much shorter than that in vacuum and diluted gas [12]. Variation of the liquids gives additional degrees of freedom in LAL process tuning to produce particles with predictable properties. Chakif et al. [13] investigated MNPs prepared by fs-LAL in water/acetone mixture, it was shown a non-monotonically influence of liquid on size and chemical composition of MNPs, and thus on magnetic properties. In this way, particles were ob- tained in the range of 30–48 nm, with a maximum coercive of 170 Oe at room temperature in 50/50 water/acetone mixture. It was also observed that the decrease of water concentration reduces the amount of antiferromagnetic phase (FeO), at the same time, there was an increase of FexCy phase. Laser beam power is one of factors that can affect the nanoparticles formation, that parameter increase can lead to prepared particles size change [8]. In papers [14] and [6] it was shown that the size of ablated particles decreases with laser beam power increase. 109