Shinichiro Kondo1, Eiji Kita2, Kiiti Siratori3 and Hiromitsu Ino4
1Graduate Student, The University of Tokyo, Tokyo
Melt-spun La100-xFex alloys (x =1, 4, 8) have been investigated by magnetization, X-ray diffraction and the Mössbauer effect. The lattice constant of the fcc β-La phase predominantly quenched is independent of iron content and the increment is less than 0.2% compared with that of pure La. A quadrupole doublet with a splitting of 0.44 mm/s is observed in the Mössbauer spectra measured at 300 K. The above results suggest that most of iron atoms are not solved in the fcc lattice but clustered each other. The inverse magnetic susceptibility 1/χ shows the formation of ferromagnetic clusters containing about 100 iron atoms in average.
Magnetization measurements show that ferromagnetic transition occurs at about 300 K and that there exists superparamagnetism between 300 and 400 K. We propose a model that the clusters interact each other and the ferromagnetic behaviour is attributed to the cluster-cluster interaction. Based on molecular field approximation, we conclude that experimental results can be explained as a system of the clusters with the average magnetic moment of 200 to 230 μB and the Curie temperature of 270 to 290 K.
melt-spinning, iron-lanthanum alloy, magnetization, Mössbauer effect, cluster, Curie-Weiss law, superparamagnetism, molecular field approximation
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