ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Ferrite plating facilitates the formation of polycrystalline spinel films in an aqueous solution below 100 °C. The plating temperature can be extended up to 200 °C when the pressure of the reaction solution is kept high (15–20 kgf/cm2). We call this "hydrothermal ferrite plating,'' by which solubility limit of Ni in Fe3−xNixO4 increases much, from x=0.3 (by conventional ferrite plating at 90 °C) to x=0.93.1 In this paper we describe preparation of Fe3−xCoxO4 films by the hydrothermal ferrite plating at T=120–200 °C and p=15–40 kgf/cm2, and report their structural and magnetic properties. Plating for 1 h, we obtained films about 1 μm in thickness, which are polycrystalline with no preferential crystal orientation as observed by x-ray diffraction. The solubility limit of Co, which is x=0.6 at 90 °C, increases to x=1.3 at 180 °C. The solubility limit of Co is higher than that of Ni, which may be because Ni tends to keep 2+ state in the spinel structure, while Co can take both 2+ and 3+ states. When prepared at 200 °C, the saturation magnetization of the films are smaller than that reported for bulk samples, though both agree when the films are prepared at 90 °C.2 This suggests that Co is oxidized to 3+ state even when x〈1.0 as large as the Fe3−xCoxO4 films are prepared in the hydrothermal conditions. We found that adding CH3COONH4 into the reaction solution as a pH buffer improves the smoothness of the film surface.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.349924
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