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

B. V. Vasil'ev ; R. Yu. Smyslov ; D. A. Kirilenko ; A. N. Bugrov

Nanosistemy: fizika, himiâ, matematika, Tome 12 (2021) no. 4, pp. 492-504

Résumé

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 Co$_x$Fe$_{3-x}$O$_4$ 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. Co$_x$Fe$_{3-x}$O$_4$ 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$^\circ$C, 7 MPa for 10 hours.

Détail

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