Magnetic properties of nanosized Delta g-Fe2O3 and Delta a-(Fe2/3Cr1/3)2O3, prepared by thermal decomposition of heterometallic single-molecular precursor

• Published in: Journal of magnetism and magnetic materials Vol. 324; no. 4; pp. 595 - 601
• Main Authors: Vasylenko, I V, Kolotilov, S V, Kotenko, I E, Gavrilenko, K S, Tuna, F, Tim&#, o, G A, Winpenny, R E P, Pavlishchuk, V V
• Format: Journal Article
• Language: English
• Published: 01-02-2012
• Subjects: Coercive force; Defects; Magnetic properties; Magnetization; Nanomaterials; Nanoparticles; Nanostructure; Thermal decomposition
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2011.08.049

Thermal decomposition of the trinuclear complex [Fe2CrO(CH3COO)6(H2O)3]NO3 at 300, 400 and 500 ?C gave Delta *g-Fe2O3 nanoparticles along with amorphous chromium oxide, while decomposition of the same starting compound at 600 and 700 ?C led to the formation of Delta *a-(Fe2/3Cr1/3)2O3 nanoparticles. Size of Delta *g-Fe2O3 nanoparticles, determined by X-ray diffraction, was in the range from 9 to 11 nm and increased with formation temperature growth. Average size of Delta *a-(Fe2/3Cr1/3)2O3 nanoparticles was about 40 nm and almost did not depend on the temperature of its formation. Delta *g-Fe2O3 nanoparticles possessed superparamagnetic behavior with blocking temperature 180--250 K, saturation magnetization 29--35 emu/g at 5 K, 44--49 emu/g at 300 K and coercivity 400--600 Oe at 5 K. Delta *a-(Fe2/3Cr1/3)2O3 nanoparticles were characterized by low magnetization values (2.7 emu/g at 70 kOe). Such magnetic properties can be caused by non-compensated spins and defects present on the surface of these nanoparticles. The increase of Delta *a-(Fe2/3Cr1/3)2O3 formation temperature led to decrease of magnetization (being compared for the same fields), which may be caused by decrease of the quantity of defects or non-compensated spins (due to decrease of particles' surface).