Properties of cobalt ferrites grown by chemical transport

Authors:

• Henryk Szydłowski,
• H. Lübbe,
• P. Kleinert

Abstract

Starting from the corresponding mixture of powdered oxides CoO, Fe₂O₃, and Fe₃O₄, cobalt ferrites of composition Co_xFe_3‐xO₄ (0 ≦ x ≦ 1) were transported with HCl in a closed system from higher (1000°C) to lower temperatures (900°C). Crystals grown to a size of up to 5 mm at the colder end of the ampoule were chemically analysed and characterized by measurement of the magnetic moment and Curie temperature. The composition of oxides in the transported crystals is found to deviate by about 1 to 2% from the initial powder mixture. Especially remarkable is the smaller cobalt content of the crystals. The dependence of the magnetic moment on the chemically proved composition is in good agreement with crystals grown by flame fusion, whereas other values found in the literature differ. The magnetic moments of the residual initial material differ slightly from those of crystals separated from the gaseous phase. The dependence of Curie temperature on composition is in agreement with results of other authors and points to single‐phase ferrite monocrystals in the investigated region. Copyright © 1970 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim