Abstract
Pure and crystalline EuO is a well known ferromagnetic semiconductor with Tc = 67 K. If Gd substitutionally replaces Eu, the Gd acts as a donor, and one obtains an increase in conductivity and of Tc. If the Gd concentration is of the order of percents, Gd clusters begin to form. Within the clusters the energy levels of the donor may be degenerate with the bottom of the conduction band, and outside a cluster localized donor states may still exist. Since the ionic radii of Gd3+ and Eu2+ are different, local distortions will further modify the energy levels. The energy of the bottom of the conduction band and possibly also the 4f-states will thus be warped as a function of the spatial coordinates. As a consequence, these materials will display an “amorphous” behavior. It is the purpose of this paper to cite various experiments concerning the optical, magnetic and conducting properties to prove that these materials can indeed be assumed amorphous, in spite of the fact that the X-ray pattern clearly shows crystalline structure.
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© 1973 Plenum Press
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Wachter, P. (1973). Long and Short Range Magnetic Interactions and Electric Switching in Highly Doped, “Amorphous” Ferromagnetic Semiconductors. In: Hooper, H.O., de Graaf, A.M. (eds) Amorphous Magnetism. Springer, Boston, MA. https://doi.org/10.1007/978-1-4613-4568-8_12
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