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SIZE-CONTROLLED SYNTHESIS OF CoFe2O4 NANOPARTICLES FOR DATA STORAGE APPLICATIONS. Preliminary results evidenced the strong influence of synthesis conditions on the magnetic properties of produced ferrites nanoparticles. M-H curves at 300K for CoFe2O4 produced under two different heating conditions (temperature of the hot plate during synthesis) and 5 h of reaction time showed the variation in coercivity  from 35  Oe at 330oC (Figure 1-a) up to 150 Oe when the plate temperature was 400oC (Figure 1-b). This raise in coercivity was attributed to the further growth of the ferrite crystals at expenses of the dissolution of the smaller ones (Oswald’s ripening effect). The inset shows the part of the plot near to the origin. Ongoing work is focused on the optimization of synthesis conditions for the ferrite nanoparticles to be used as seeds in a subsequent precipitation step. Seeding is expected to improve the control of nanocrystal size and hence, higher values in room temperature coercivity.

 

 

 

 

 

 

 

 

 

 

  

 ROOM-TEMPERATURE SYNTHESIS AND CHARACTERIZATION OF MONODISPERSE ZnO-BASED NANOSTRUCTURES FOR SPINTRONICS APPLICATIONS: Initial results demonstrated the viability on producing well-crystallized and highly monodisperse ZnO nanocrystals at room temperature (25 oC). The formation of the ZnO structure was delayed when Mn or Co ions co-existed in starting solutions. The growth of the nanocrystals during aging can be inhibited by their fast coagulation by n-heptane. SQUID analyses suggest the actual incorporation at room temperature of Mn and Co ions into otherwise diamagnetic ZnO structure. A weak ferromagnetism was observed at room temperature for as-synthesized (i.e., no thermal treatment nor aggregation was needed) @ 6nm Co-ZnO crystals (x = fraction of dopant ion in starting solution = 0.01). Currently, our effort are oriented to the optimization of achieved ferromagnetism at room temperature as well as investigate other oxides- and calcogenides-based systems.

 

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