Abstrakt
In magnetism of nanoparticles, surface spin effects play a key role. The so-called spin canting at the surface leads either to lowering of saturation magnetization, or even to lack of saturation in high magnetic elds.
The value of the saturation magnetization depends on cation distribution within the spinel network and on the spin canting angles. We have investigated structure and magnetic behavior of CoFe2O4 nanoparticles doped with La (Co1-xLaxFe2O4, x = 0.05 - 0.5 and CoLaxFe2-xO4, x = 0.05 - 0.2) embedded in amorphous silica matrix prepared by a sol-gel method.
The samples were characterized using X-ray diraction and TEM. The zero-eld cooled and eld cooled measurements of magnetization showed that the blocking temperature is well above the room temperature.
The high coercivity was observed (up to 2 T at 10 K) and no saturation of the magnetization even in applied eld of 7 T was obtained, suggesting considerable spin canting effects. Finally, the Mossbauer spectroscopy under magnetic eld and down to low temperature was performed to determine the cation distribution and the spin canting angles.