• Babic-Stojic, B.
• Jokanovic, V.
• Milivojevic, Dusan
• Jaglicic, Z.
• Cupic, S.
• Kojic, D.
• Jovic, N.
• Colovic, B.
• Brankovic, D.

Abstract

<jats:p>The magnetic properties of mesoscopic materials are modified by size andsurface effects. We present a sol-gel method used to tailor these effects,and illustrate it on Co1+yAl2-yO4 spinel. Nanocomposites made of spinel oxideCo1+yAl2-yO4 particles dispersed in an amorphous SiO2 matrix weresynthesized. Samples with various mass fractions -x of Co1+yAl2-yO4 incomposite, ranging from predominantly SiO2 (x = 10 wt%) to predominantlyspinel (x = 95 wt%), and with various Co concentrations in spinel y werestudied. The spinel grain sizes were below 100 nm with a large sizedistribution, for samples with predominant spinel phase. Those samples showedCurie-Weiss paramagnetic behavior with antiferromagnetically interacting Coions (? ? -100 K). The grain sizes of spinel stays confined in 100 nm rangeeven in the spinel samples diluted with as low as 5 wt% concentration ofamorphous SiO2. For the samples with predominant SiO2 the crystallinenanoparticles are well separated and of size of around 100 nm, but withpresence of much smaller spinel nanoparticles of about 10 nm. The magneticproperties of the samples with predominant silica phase showed complexbehavior, spin-glass magnetic freezing at the lowest temperatures and lowerabsolute value of ? and consequently lower exchange constant.</jats:p>

Topics

• nanoparticle
• nanocomposite
• amorphous
• grain
• grain size
• phase
• glass
• glass