Magnetism of Surface-Modified and Gallium-Doped Magnetite Particles
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agnetism of Surface-Modified and Gallium-Doped Magnetite Particles K. Rećkoa, *, D. Satułaa, J. Waliszewskia, b, M. Biernackaa, M. Orzechowskaa, B. Kalska-Szostkoc, D. Soloviovb, d, e, A. Miaskowskif, A. Beskrovnyyb, A. Basac, and K. Szymańskia aFaculty
of Physics, University of Bialystok, Białystok, 15-245 Poland Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, Moscow oblast, 141980 Russia c Faculty of Chemistry, University of Bialystok, Białystok, 15-245 Poland d Moscow Institute for Physics and Technology, Dolgoprudny, Moscow oblast, 141701 Russia e Institute for Safety Problems of Nuclear Power Plants, National Academy of Sciences of Ukraine, Chornobyl, Kyiv, 07270 Ukraine f Department of Applied Mathematics and Computer Science, University of Life Sciences in Lublin, Lublin, 20-950 Poland *e-mail: [email protected] b
Received July 5, 2019; revised July 31, 2019; accepted August 10, 2019
Abstract—New data on gallium ferrite particles are reported. The results of studies of Fe3O4/GaxFe3 – xO4 and GaxFe3 – xO4/Fe3O4 (x = 0.2, 0.4, 0.6 and 0.8) nanoparticles by X-ray and neutron diffraction, small angle neutron scattering, transmission electron microscopy, magnetization measurements, and Mössbauer spectroscopy. The cubic core–shell ferrites structures were confirmed as single phases with a cell parameter of ∼8.388 Å independent of gallium content. The lack of preferences in occupancies of gallium sites was confirmed. The magnetic structure at room temperature, the stability of a disaggregated dispersion of nanoparticles in the temperature range 20–50°C, the radii of the cores, and the thickness of the coating layers, as well as the specific absorption of electromagnetic radiation rates were characterized. Keywords: magnetic nanoparticles, superparamagnetism, specific absorption rate, X-ray diffraction, neutron diffraction, Mössbauer spectroscopy, calorimetric measurements, magnetization measurements DOI: 10.1134/S102745102007040X
INTRODUCTION Nanoferrites with a cubic crystal structure form a group of innovative materials with wide application prospects [1]. The growing interest in nanotechnology is driving the development of a wide variety of isostoichiometric materials of different shapes on a nanometer scale. Small angles neutron scattering (SANS) and transmission along with scanning electron microscopy (TEM, SEM) measurements confirm the change in shape of nanoparticles from the parallelepiped to spherical [2]. This paper concentrates on gallium ferrites, which are magnetic nanoparticles of core–shell type. Magnetic nanoparticles can be obtained by various chemical techniques and, therefore, require the use of an appropriate surface stabilizer and solvent. The latter should be compatible with the inorganic core [3]. If nanoparticles are dispersed in organic solvents (diphenyl ether, toluene, etc.), oleic acid or oleylamine are used as surfactants [4, 5]. The GaxFe3 – xO4 nanoparticles (x = 0.2, 0.4, 0.6, 0.8) in the form of a shell or as a core coated with magnetite crystall
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