The Research On The Self-assembly Growth And Magnetic Properties Of The Magnetic Metal Nanoparticles

With the rapid development of nanotechnology, nanomaterials,especially magnetic nanoparticles，have aroused researchers’ greatinterest. Magnetic nanoparticles is a kind of intelligent nano material,which not only have the properties of the surface effect and quantumsize effect unique to nano material but also have the properties ofmagnetic responsiveness and superparamagnetism. The structureand properties of nanoparticles are closely linked with the shape, sizeand the uniformity distribution of the particle. Therefore, synthetizingnanoparticles with perfect shape, unified size and perfectmonodispersity has become the hotspot of the researchers. Usingpulsed laser deposition and magnetron sputtering system, We grewunrestricted Fe nanoparticle, incomplete limited Co nanoparticlesand completely restricted FePt nanoparticle self-assembly ondifferent substrates and discussed the morphology, structure andmagnetic properties of nanoparticles and self-assemble growth mechanism in this paper. As a result, the free growth of the size,shape and the distribution of the nanoparticles to fully controllablegrowth were realized in the end. The main research content is asfollows:（1） Using pulsed laser deposition technique，we deposited45nmLa0.7Ca0.3MnO₃film with perovskite structure as the buffer layer todeposit Fe nanopartical on the SrTiO₃（001） substrate. Weself-assembly grew two different Fe nanoparticles with the thicknessof0.5nm and1.5nm respectively on the surface of buffer layer. Thesurface morphology and magnetic properties of nanoparticles wereresearched respectively using atomic force microscopy andsuperconducting quantum interference device, The results show thatwhen the thickness of Fe was0.5nm, Fe nanoparticle with theuniform distribution,30nm average diameter and5nm vertical heightwas formed on the surface of the La0.7Ca0.3MnO₃buffer layer, However,when the thickness of Fe was1.5nm, nanoparticles without uniformdistribution was observed. The whole saturation magnetization andCurie temperature of the samples both decreased after depositing Fenanoparticle.（2） Using the magnetron sputtering device, films of two typesstructure, the ultra-thin Co/ZnO and Co/ZnAlO （Al:2at.%） wereprepared at room temperature adopting the method of continuous layered alternating deposition. The results showed that films of twotypes were with similar structure and both generated films in whichCo nanoparticles were dispersed in ZnO（ZnAlO） matrix. The diameterof the Co nanoparticles was between3and6nm, which was far lessthan the size directly synthesis on a substrate. This is mainly due tothe fact that the semiconductor ZnO matrix, deposited in the processof the growth of the nucleation of Co nanoparticles, effectively limitedthe growth of Co nanoparticles when using the method of continuouslayered alternating deposition. In addition, there was no obviousinterface separation between Co nanoparticles and semiconductorZnO matrix, which may result from the fact that parts of the electronof the ZnO semiconductor were polarized by metal cobalt andgradient magnetic semiconductor was formed in the interface region.Two types of thin film, Co/ZnO and Co/ZnAlO, were both withsurparamagnetic at room temperature. Besides, the addition of Alincreased the carrier concentration, so that the magnetic andmagnetic resistance effect of Co/ZnAlO was improved at the sametime.（3） With the method of the combination of the template-magnetron sputtering, FePt nanoparticle was self-assembly grew onthe ultra-thin anodic aluminum oxide template of different aperture tostudy the regulation of its growth. Meanwhile, the composition, structure and magnetic properties of nanoparticles were analyzedcomparatively through combining FePt film with the same calibrationthickness. The results show that using the template method,nanoparticals with good monodispersity were synthesized, whosegeometric shapes and sizes were both consistent with and the shapesand diameter of the pores in the AAO template to achieve the fullycontrollable growth. FePt nanoparticles, deposited in the amorphoussubstrate, were those with FCC structure, perfect dispersibility andferromagnetism at room temperature. Meanwhile, the coercive forcedecreases with the increase of the geometry size of the nano particle.All in all, the free growth of the nanoparticles to fully controllablegrowth was realized using self-assembly technology and differentmethods. The relationship between the distribution and the geometricsize of nanoparticles and magnetism was studied, which not onlyhelps to further understand the growth mechanism of nanoparticlesand magnetic sources, but also are of great importance to expand itsapplication field.