Magnetic Properties of Splat-Cooled Fe-Co-V Alloys

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Abstract
Previous investigations showed that the magnetic properties of Fe‐Co‐V alloys were susceptible to the speed of quenching and therefore it was thought that splat cooling might give further insight into their magnetic behavior. Accordingly, alloys having contents from 0% to 20% vanadium with 52% cobalt and the remainder iron were splat‐cooled. Coercive forces of 850 Oe which are high for this system were obtained on splat‐cooled specimens having 20% V after an aging treatment. A rather puzzling phenomenon was observed on splat‐cooled samples of alloys in the vicinity of 14% V; at 300°K, the specimens acted in a paramagnetic manner, but upon cooling down to 1.4°K, they became ferromagnetic. The increase in magnetization cannot be attributed to an increase in the α phase since this transformation is irreversible, and in this case the magnetic properties are reversible on cooling and heating. This behavior could be explained, however, if there were a large number of superparamagnetic particles present. Electron micrographs were taken which showed particles of less than 50 Å in diameter. Furthermore, upon aging at 500°C, particles of a much larger size were observed (several hundred angstroms), the specimens then became ferromagnetic at room temperature and the large increase in magnetization by cooling to low temperatures disappeared.

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