"Nanotechnology and nanomaterials"

Structure and magnetic properties of superparamagnetic      La0.8-xGdxNa0.2MnO3 nanoparticles
Liedienov N.A.1,2, Bodnaruk A.V.3, Fesych I.V.4, Pashchenko A.V.1,2,5,6
1 International Centre of Future Science, State Key Laboratory of Superhard Materials of Jilin University. Qianjin Str., 2699, Changchun-130012, China.
E-mail: nikita.ledenev.ssp@gmail.com
2 Phase Transitions Department, Donetsk Institute for Physics and Engineering named after O. O. Galkin, NASU. Prospect Nauki, 46, Kyiv-03028, Ukraine.
3 Institute of Physics, NAS of Ukraine. Prospect Nauki, 46, Kyiv-03028, Ukraine.
4 Taras Shevchenko National University of Kyiv. Lva Tolstoho Str., 12, Kyiv-01030, Ukraine.
5 Institute of Magnetism, NASU and MESU, 36-b Vernadsky Blvd., Kyiv-03142, Ukraine.
6 Ivano-Frankivsk National Technical University of Oil and Gas, MESU, 15 Karpatska Str., 76019 Ivano-Frankivsk, Ukraine.

Magnetic metal oxides with a perovskite structure are perspective and topical materials which are actively used in various areas of science and technology. The La-substituted La0.8-xGdxNa0.2MnO3 manganites with x = 0 and 0.05 were synthesized using a sol-gel auto-combustion method. According to the X-ray powder diffraction data, it has been found that a mixture of La2O2CO3, Mn3O4 and NaNO2 is formed after the auto-combustion process of nitrate-citrate gel. At a temperature of 500 °C, a single-phase product with a rhombohedral perovskite structure is formed. An average crystallite size calculated using Scherrer’s formula for peak (012) for the pure lanthanum manganites is 35 nm (500 °C), 63 nm (700 °C), and 97 nm (900 °C), respectively. As the temperature increases, there is a slight increase in the volume of the unit cell and in X-ray density that indicates a decrease in the defect structure due to reducing the amount of oxygen vacancies. According to magnetostatic studies conducted at room temperature, the             La0.8-xGdxNa0.2MnO3 samples with x = 0 and 0.05 at tsynth> 500 °C demonstrate the typical behavior of an ensemble of superparamagnetic nanoparticles. As tsynth increases, an increase in the saturation magnetization from 0 emu/g for x = 0 and 0.05 (500 °C) to 20 emu/g for x = 0 (700 °C) and 48 emu/g for x = 0.05 (900 °C) is observed.