Abstract
The mass susceptibility ((mass)) and mass magnetization (M-mass) were determined for a series of ternary manganese and zinc ferrite nanoparticles (Mn-Zn ferrite NPs, MnxZn1-xFe2O4) with different Mn:Zn ratios (0.08 x 4.67), prepared by the thermal decomposition reaction of the appropriate metal acetylacetonate complexes, and for the binary homologs (MxFe3-xO4, where M = Mn or Zn). Alteration of the Mn:Zn ratio in Mn-Zn ferrite NPs does not significantly affect the particle size. At room temperature and low applied field strength the mass susceptibility increases sharply as the Mn:Zn ratio increases, but above a ratio of 0.4 further increase in the amount of manganese results in the mass susceptibility decreasing slightly, reaching a plateau above Mn:Zn approximate to 2. The compositional dependence of the mass magnetization shows less of a variation at room temperature and high applied fields. The temperature dependence of the mass magnetization of Mn-Zn ferrite NPs is significantly less for Mn-rich compositions making them more suitable for downhole imaging at higher temperatures (>100 degrees C). For non-shale reservoirs, replacement of nMag by Mn-rich Mn-Zn ferrites will allow for significant signal-to-noise enhancement of 6.5x over NP magnetite.