Synthesis and Magnetic Characterization of Mn and Co Spinel Ferrite-Silica Nanoparticles with Tunable Magnetic Core

Abstract

A method for coating silica on CoFe2O4 and MnFe2O4 spinel ferrite nanoparticles has been developed by using a reverse micelle microemulsion approach. The ability to controllably synthesize magnetic nanoparticulate cores independent of encapsulation provides great flexibility in tuning the magnetic properties of this magnetic nanocomposite system by controlling the magnetic properties of nanoparticulate cores. For these spinel ferrite nanoparticles, the saturation and remnant magnetizations decrease upon silica coating. The coercivity of silica-coated CoFe2O4 nanoparticles does not show any change after coating, while the coercivity of MnFe2O4 nanoparticles decreases by 10% after they have been coated with silica.

Applications of exchange coupled bi-magnetic hard/soft and soft/hard magnetic core/shell nanoparticles

“…Nevertheless there are many other chemical routes which, although they have not been used for hard-soft materials, have demonstrated their suitability to synthesize different types of inorganic/inorganic core/shell nanoparticles [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. For instance, microemulsion and sol-gel approaches are probably two of the most useful routes to synthesize this type of architectures [145][146][147][148][149][150][151][152]. Moreover, other more unusual methods (sometimes specific for a given system) can also be found in the literature such as one-pot sonochemical synthesis of Fe 3 O 4 /FeP core/shell nanoparticles [153] or microwave irradiation synthesis of Ni/Cu core/shell nanoparticles from initial mixed solution containing both precursors [112].…”

Application of alternative energy forms in catalytic reactor engineering

“…Metal oxide [17, 66 -70] , metallic, mainly Fe and Co [71 -73] , and bimetallic, such as FePt [74,75] MNPs have been proposed for this purpose. Many of these materials were coated, to provide an inert and biologically compatible outer shell made of silica [67] , gold [43,57,76] or carbon [71,73] . [36,48] .…”

Biomedical Applications of Multiferroic Nanoparticles

“…As seen in Figure 13b the coating of the ferrite nanoparticles with the ferroelectric layer has a substantial effect on their magnetic properties: while the 14 nm CoFe 2 O 4 nanoparticles are superparamagnetic at room temperature, CoFe 2 O 4 @PbTiO 3 core-shell nanoparticles are ferrimagnetic and present a coercivity of about 1200 Oe. This is the result of the modification of the contributions of the surface anisotropy and dipolar interactions between the adjacent nanoparticles on the average magnetic moment of the nanocomposite [74,75]. A wide variety of spinel ferrite nanoparticles can be coated with perovskite layers, such as BaTiO 3 , PbTiO 3 and Pb(Ti, Zr)O 3 and their properties can be controlled by adjusting both the size of the magnetic core and the thickness of the perovskite shell.…”