Magnetization enhancement and cation valences in nonstoichiometric (Mn,Fe) 3-δ O 4 nanoparticles

• Published in: Journal of applied physics 2012-04, Vol.111 (7), p.074309-074309-6
• Main Authors: Antic, B., Kremenovic, A., Jovic, N., Pavlovic, M. B., Jovalekic, C., Nikolic, A. S., Goya, G. F., Weidenthaler, C.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3700228

We present a study of the structural and magnetic properties of (Mn,Fe) 3- δ O 4 nanoparticles synthesized by soft mechanochemistry using Mn(OH) 2 × 2 H 2 O and Fe(OH) 3 powders as starting compounds. The resulting nanoparticles with a composition of the (Mn,Fe) 3- δ O 4 type are found to have a core/shell structure with different Mn/Fe ratios in the core and at the surface. XPS analysis points to valences of +2,+3, and +4 for Mn and +3 for Fe at the particle surface. Combined results of XRPD, Mössbauer spectroscopy, and EDX analysis suggest that there is a deviation from stoichiometry in the nanoparticle core compared to the shell, accompanied by creation of cation polyvalence and vacancies. The value of saturation magnetization, M S , of 73.5 emu/g at room temperature, is among the highest reported so far among nanocrystalline ferrite systems of similar composition.