Preparation And Properties Of CoPt Magnetic Nanomaterial

The L10CoPt phase with the FCT structure has the high magnetocrystallieanisotropy and curie temperature, better coercivity, high chemical stability, whichmake it the best candidates in the ultra-high density recording media,drug targeting vector, magnetic resonance imaging, biotechnology/biomedicine andenvironmental remediation.In this paper, CoPt nanoparticles have been synthesized by sol-gel. The structure,morphology and magnetic properties of the samples are controlled by Ag-doping,Cu-doping and SiO2addition. Ordered Co/Pt nanocap arrays are prepared bysputtering Co and Pt onto2D PS array and the easy magnetic axis is controlled by thesputtering parameter.The primary results are as following:1. We have successfully synthesized CoPt NPs with different Co concentrationsby the sol–gel method. The sol–gel method is easy and economical enough in view ofstructure control. Moreover, the precursor is non-toxic and we can easy to control it.The XRD results show that L12CoPt3is formed at the Co concentration ranging from25to40at.%. The ordered CoPt structure with a L10phase is formed at the Coconcentration ranging from50to60at.%. When the Co concent reaches75at.%, theFCC Co3Pt phase is formed. TEM images are consistent with the XRD results. VSMresults show that Hc increases with the increased content of Co, and the Hc reaches amaximum at50at.%Co and then decreases. Moreover, the order parameter has aneffect on the magnetic properties of the CoPt NPs.2. The pure CoPt and the CoPt–Cu NPs (various Cu content) are synthesized bysol–gel at various temperatures. L10CoPt and FCC CoPt3coexist in pure CoPtnanoparticles, whereas a complete L10phase forms in the CoPt–Cu nanoparticles with50at.%Cu doping when the annealing temperature is600℃. Cu is effective toreduce the ordering temperature and promotes the magnetization properties. From this point, the CoPt NPs with Cu additive is a good candidate for the applications inhigh-density magnetic recording. The L10CoPt NPs with various Ag contents aresynthesized by sol–gel after annealing at700℃. Hard and soft phases coexist inCoPt-Ag NPs when the Ag contents increase over0at.%. Hc has the maximum valueabout0.7T when the Ag content is15at.%, which is because of the increasingordering degree and particles size of the NPs. It indicates that Ag addition is effectiveto enhance the ordering degree and promote the magnetic properties of CoPt NPs.3.45o Tilted film [Pt(3nm)/Co(0.45nm)]15is fabricated on thecurved substrateof2D polystyrene template with diameter200nm. MFM measurement showed theformation of the single magnetic domain on individual, and the every isolatedmagnetic domain is separated from the neighbors. HRTEM shows the alloysformation near the multilayer film brim, which removes the coupling between thesublayers and magnetic actions between the neighbor units. The hysteresis loopsmeasurements show the tilted magnetic anisotropy axis of the multifilm on specialcurve substrate. As the result, the Co/Pt films are synthesis in spite of the curvedsurface.