NEW LASER ABLATION CLUSTER SOURCE FOR A SYNTHESIS OF MAGNETIC NANOPARTICLES, AND FMR STUDY OF Ni:MgF_2 COMPOSITES

摘要

A new technique for synthesis of Ni magnetic nanoparticles in diamagnetic matrix by using a novel laser universal cluster ablation source (LUCAS) is presented. The source has been developed specially for highly refractory materials with high melting temperatures. Ablation/evaporation laser pulses were applied to the Ni bulk target to form metal vapor in high pressure seeding Ar-gas, and then expansion of the material vapor through a nozzle with the carrier Ar gas was performed. The nickel nanoparticles deposited on a substrate surface were protected by a complementary electron sputtering of magnesium fluoride bulk material. Electron microscopy showed that a highly homogeneous dispersion of the crystalline Ni nanoparticles with a size of near 3 nm was formed in the deposited layer. The magnetic properties of the nanostructured Ni:MgF_2 composite were investigated by magnetic resonance technique in X-band (9.8 GHz) at room temperature. A highly anisotropic ferromagnetic resonance (FMR) responce of the Ni:MgF_2 composite was found. Broadening of the FMR signal, when the DC magnetic field is rotated towards the plane .of the composite, was also observed. Effective media approach to the FMR in thin granular magnetic films was applied to analyze the resonance field and linewidth dependencies on orientation, and the value of the magnetization of the synthesized Ni:MgF_2 composite was extracted.