Magnetic Properties of Mixed Cobalt-Aluminum Ferrite Nanoparticles

A. T. Raghavender ； R. G. Kulkarni ； K. M. Jadhav

《Chinese Journal of Physics》 48卷4期 (2010/08) Pp. 512-522

並列摘要

The magnetic properties of nanocrystalline CoFe(subscript 2-x)Al(subscript x)O4(0≤x≤1) spinel ferrites have been investigated by means of Mössbauer spectroscopy, using a vibrating sample magnetometer (VSM). The crystal structure was found using an X-ray diffractometer (XRD) and verified using transmission electron microscopy (TEM). Substitution of Al content x in cobalt ferrite caused a decrease in particle size, lattice parameter, and Curie temperature. The Mössbauer and VSM studies for these nanoparticles revealed the existence of a non-collinear spin arrangement at the surface of the CoFe(subscript 2-x)Al(subscript x)O4 nanoparticle. The saturation magnetization changes with increasing Al content due to the effect of cation distribution in tetrahedral and octahedral sites and due to a change in ferrimagnetic structure. The particle size effects on the coercivity at 290 K were studied. The phase change in the Mössbauer from ferromagnetic to paramagnetic with nanoparticles is due to the fact that the particles are too small to maintain the ferrimagnetic parameters.