Magnetic properties of nanosized powders of magnetic oxides synthesized bypulsed laser ablation

We present a detailed study of synthesis by pulsed laser ablation and the m agnetic characterization of nanosized powders of iron oxides and strontium ferrite. In the case of iron oxide, it is found that the particle formation and their growth take place in the gas phase before reaching the cold fing er (used as substrate for condensation). However, in the case of strontium ferrite, the as-condensed material is amorphous, and requires annealing at high temperature to induce nanoparticle growth. Very high values of intrins ic coercive field (similar to 6665 +/- 10 Oe) are realized for the strontiu m ferrite powder having an average particle size of about 35 nm. The temper ature variation of coercive field and remanence of the nanosized powders is found to be substantially different from those of the corresponding bulk m aterials. (C) 2000 American Institute of Physics. [S0021- 8979(00)02815-2].