Magnesium‐manganese‐aluminum ferrites prepared by dry pressing techniques are usually fired in the temperature range between 1350 and 1400°C for extended periods of time to obtain samples having high relative densities. When about ten percent of the magnesium in such a system is replaced by copper, as in the series Mg0.9Cu0.1AlxFe1.75−xMn0.04O4±, it is possible to obtain samples with high relative densities and dc resistivities by firing in the 1250 to 1300°C range. Such materials are suitable for microwave applications.The preparation of ferrites of this type is discussed and data presented on the saturation inductions, Curie temperatures, densities, and dc resistivities.