Ferro-, Antiferro-, and Superparamagnetic Behavior of Fe-Al Alloys

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Abstract
In agreement with measurements of Sato and Arrott, and of Kouvel, we also found anomalous magnetic properties of Fe-Al alloys containing more than 28 at.%. Al. In order to investigate the different properties of these alloys in more detail, we have measured the temperature dependence of magnetization, susceptibility, anisotropy, rotational hysteresis, and coercive force of monocrystalline and polycrystalline specimens (containing 28 to 50 at.% Al) between 1.5° and 300°K. The following results have been found: a maximum of rotational hysteresis at about 12°K, high coercive forces and high unidirectional and uniaxial anisotropy in the temperature region below 40°K, magnetization creeping between 4° and 50°K, and superparamagnetic-like behavior at higher temperatures. These results may be interpreted by assuming the existence of two phases one of which is ferromagnetic, the second antiferromagnetic below 40°K. For T∼40°K, the domains of one phase, and for lower temperatures, the domains of both phases interact.