Crystallographic and magnetic properties of Cu2U-type hexaferrite

• We have synthesized the crystallographic single-phase Cu2U-type hexagonal ferrite.
• MS is found to be 46.8 A·m2/kg at 300 K and 65.0 A·m2/kg at 5 K.
• TC is 420°C. It is lower than TCM-type (450°C) but higher than TCCu2Y-type (320°C).
• The estimated saturation magnetization is consistent with experimental MS at 5 K.

We have investigated the synthesis conditions, and the magnetic properties of the Cu2U-type hexagonal ferrite, Ba4Cu2Fe36O60. The Cu2U-type hexaferrite was synthesized at the sintering temperature of 1050 °C with the initial composition of Ba4.4Cu2Fe37.6O62.8 (Cu2U+0.2T-block). The saturation magnetizations at 300 K and 5 K are 46.8 A m2/kg and 65.0 A m2/kg, respectively. The Curie temperature is 420 °C which is lower than that of the M-type ferrite (450 °C) but higher than that of the Cu2Y-type ferrite (320 °C). The amount of the nonmagnetic impurity in this sample is estimated to be about 10 wt% by the electron probe micro analysis. We estimated the expected saturation magnetization to be 65.2 A m2/kg, by assuming the model of a Néel-type ferrimagnetic structure and the reduction of magnetization by the 10 wt% nonmagnetic impurity. This is consistent with the observed magnetization of 65.0 A m2/kg at 5 K.