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NANOSYSTEMS: PHYSICS, CHEMISTRY, MATHEMATICS, 2021, 12 (4), P. 492–504

Synthesis and magnetic properties of cobalt ferrite nanoparticles formed under hydro and solvothermal conditions

B.V. Vasil’ev – Institute of Macromolecular Compounds RAS, Bolshoy pr. 31, 199004 Saint Petersburg; Saint Petersburg Electrotechnical University “LETI”, ul. Professora Popova 5, 197376 Saint Petersburg, Russia; boris8152@gmail.com
R.Yu. Smyslov – Institute of Macromolecular Compounds RAS, Bolshoy pr. 31, 199004 Saint Petersburg, Russia; urs@macro.ru
D. A. Kirilenko – Ioffe Institute RAS, Politekhnicheskaya ul. 26, 194021 Saint Petersburg; ITMO University, Kronverskii avenue 49, 197101 Saint Petersburg, Russia; demid.kirilenko@mail.ioffe.ru
A. N. Bugrov – Institute of Macromolecular Compounds RAS, Bolshoy pr. 31, 199004 Saint Petersburg; Saint Petersburg Electrotechnical University “LETI”, ul. Professora Popova 5, 197376 Saint Petersburg, Russia; alexander.n.bugrov@gmail.com

Cobalt ferrite nanoparticles were synthesized both in hydro and in solvothermal conditions from Co and Fe salts of different chemical nature (nitrates and chlorides) taken in a 1:2 cation ratio. Varying the chemical prehistory, synthesis temperature, isothermal holding time, and the reaction medium composition made it possible to obtain a set of CoxFe3-xO4 nanoparticles of different average diameters and isomorphic substitution degree x. The resulting nanoparticles’ elemental composition, crystal structure, sizes, and magnetic properties were determined using EDX analysis, X-ray diffraction, transmission electron microscopy, and SQUID magnetometry. The temperature dependences of the coercivity, remanent magnetization, squareness on both the average diameter and the stoichiometry of nanoparticles are considered. CoxFe3-xO4 nanocrystals ranged from 11 to 29 nm were single magnetic domains and showed ferrimagnetic behavior at room temperature. The hardest magnetic nanoparticles with maximum squareness values in the high-temperature region were formed with x = 0.79 using solvothermal treatment of cobalt and iron nitrates at 250 °C, 7 MPa for 10 hours.

Keywords: single-domain cobalt ferrite, ferrimagnetic nanocrystals, size-controlled synthesis, stoichiometry, Rietveld refinement, coercive field,
saturation magnetization, squareness.

PACS 75.20.-g; 75.75.+a

DOI 10.17586/2220-8054-2021-12-4-492-504

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